Friday wrap-up: various links...

Wherein I list some (mostly) recent happenings, ramble a bit, and provide links, in an order roughly determined by importance and relevance to particle physics. Views are my own. Content very definitely skewed by my own leanings and by papers getting coverage, and it may not even be correct. It is a blog after all..

Slow news week, or maybe I was just too busy...?

• LHC is doing 13 TeV physics again, now with 25ns bunch spacing.

• The LHCb pentaquark discovery has been published in PRL. There's a Viewpoint article from Kenneth Hicks here.

• The BOOST2015 7th International Workshop on Boosted Object Phenomenology was on this week (indico/hashtag).

• The 43rd SLAC Summer Institute is going on at the moment: The Universe of Neutrinos (indico).

• Blog post at Backreaction: Why do some people assume that the Planck length/time are the minimum possible length and time?

• John Preskill muses on Kitaev, Moore, and Read's shared ICTP Dirac Medal and anyons, the two-dimensional cousins to our fermions and bosons.

• A couple of articles from Shannon Hall at Nautilus: Is It Time to Embrace Unverified Theories? and; 6 Graphs That Showed Landmark Discoveries—but Were Later Debunked.

• In video/audio media:
• Symmetry, a dance-opera film, premiered this week; trailers at the link.
• Big Bang Aftershock, on the BICEP2 discovery and fallout. [40 minutes]
• Uranium: Twisting the Dragon's Tail. Hosted by Derek from Veritasium, and researched by my officemate Rebecca Leane! [Link for Australians; 50 minutes]
• How Does Symmetry Shape Nature’s Laws? from Quanta. [2 minutes]
• What is Dark Matter and Dark Energy? for laymen, from Nova Project. [6 minutes]
• What Has New Horizons Taught Us About Pluto? at It's Okay to be Smart. [6 minutes]
• Prime knots at Numberphile. [7 minutes]
• Tour Ceres, from Nasa JPL. [2 minutes]

• On 13 Aug, Rosetta witnessed Comet 67P/Churyumov–Gerasimenko traversing its perihelion.
  
  
  
  
  
  
• Those in the Northern Hemisphere were lucky to have an almost-new moon for the Perseids this year. (The shot below is from Ruslan Merzlyakov).
  
  
  
  
  Check out the slideshow at space.com.

Friday wrap-up: SHiP, portals...

Wherein I list some (mostly) recent happenings, ramble a bit, and provide links, in an order roughly determined by importance and relevance to particle physics. Views are my own. Content very definitely skewed by my own leanings and by papers getting coverage, and it may not even be correct. It is a blog after all...

• The SHiP fixed target experiment has uploaded its 200+ page physics case to the arXiv. Working at the intensity frontier, fixed target experiments collide very many (in this case) protons on a heavy target, with a detector placed some distance away after a significant amount of shielding. Because of the sheer number of protons on target, the setup is particularly sensitive to any ≲GeV scale extremely weakly interacting particles (large number × small number = detectable number!). The document is very comprehensive and speaks for itself; evidently the experiment has the capacity to explore some very interesting new physics scenarios, for example...
  
  If one modestly extends the standard model with a vector or a scalar field, it is always possible to write down gauge-invariant operators$$\epsilon F^{\mu\nu}F'^{\mu\nu},\\ \xi\phi^\dagger\phi S^2,$$where $F'^{\mu\nu}$ is a dark field strength operator and $S$ is a real singlet scalar. These are known as portal operators, and in the limit of very small $\epsilon$ or $\xi$ (which restores an enhanced Poincare symmetry and is therefore technically natural) the new states (referred to often as the dark photon and dark Higgs) are very long-lived and very weakly coupled to standard model states, so that they could still have gone undetected even if their masses are sub-GeV. If dark matter couples directly to these new states then they provide a "portal" from the standard model to the dark sector.
  
  So I was very interested to see the reach of the proposed experiment with respect to those portals; that reach is shown below as a function of mass for the case without dark matter, or with $m_{DM}>m_{A},m_S$ (the g* in the singlet case is proportional to the $\xi$ parameter above)...
  
  
  
  
  
  

  It is evident that the experiment would explore a significant amount of unexplored (not grey) parameter space (and the results are even stronger for a pseudoscalar). For the dark scalar case, the reach of the experiment comes from the unprecedented (in a fixed target experiment) number of B mesons produced, which can then subsequently decay to the light scalar state at a rate of one in a million or so. The states then live long enough to travel through the (~70m of) shielding before decaying in the detector.
  
  It is of note that unfortunately the widths and branching ratios of the scalar in the region $2m_\pi < m_S \lesssim 4$ GeV have large hadronic uncertainties, and the plot above must assume one theoretical prediction, so the story is not as clear-cut as it seems; luckily the experiment would be sensitive to many final states, and this goes some way to making the reach independent of this uncertainty. (These uncertainties do not exist for the dark photon thanks to measurements of our very own photon!). The most recent theoretical calculation for the dark scalar widths in this region is >20 years old. I wonder if lattice QCD could have something to say if it was applied to the problem?

• Quanta Magazine has a couple of interesting articles this week; on artificial intelligence, and entangled wormholes (first instalment of a series).

• Scientific American has an article on self-interacting dark matter on the back of the Abell 3827 cluster "hint" from last week.

• In video/audio media:
• Can LHC black holes destroy the universe? from Sabine Hossenfelder.
• CERN on LHCb and societal impacts. [2 and 4 minutes]
• Learning and unlearning to ride a reverse bike at SmarterEveryday. [8 minutes]
• The Cheryl Logic Problem at Numberphile. [11 minutes]
• First of Hubble memorable moments series. [5 minutes]
• The moment and a timelapse of the Calbuco eruption.

• NASA and ESA (and others!) are celebrating Hubble's 25th anniversary.
  
  
  

• And now that we have warmed up with Hubble here are some photos from the week...

• ... of the Calbuco eruption from Philip Oyarzo...
  
  
  
  

• ... Comet 67P/Churyumov–Gerasimenko from all the angles...
  
  
  

• ... and a glimpse of Ceres' bright spot from up close [gif].
  
  
  

Friday wrap-up: ATLAS on-Z excess, CMS kinematic edge, new dwarfs, dark matter annihilation...

Wherein I list some (mostly) recent happenings, ramble a bit, and provide links, in an order roughly determined by importance and relevance to particle physics. Views are my own. Content very definitely skewed by my own leanings and by papers getting coverage, and it may not even be correct. It is a blog after all...

• ATLAS released a preprint yesterday (submitted to EPJC), Search for supersymmetry in events containing a same-flavour opposite-sign dilepton pair, jets, and large missing transverse momentum..., that is interesting for two reasons.
  
  1. Remember the 2.6σ kinematic edge excess that CMS observed in their similar analysis originally released as a PAS in August last year? If not then see Tommaso Dorigo or Collider Blog for a summary... or don't, since ATLAS don't see any hint of it!
  
  2. They call CMS's excess, and then they raise, with a 3.0σ excess in a different signal region (SR). So let's talk about that...
  
  The search is for an on-Z opposite-sign same-flavour (OSSF) lepton pair + jets + MET. They are motivated by a gravitino LSP SUSY scenario with pair-produced gluinos which decay via $\tilde g\to qq\tilde\chi_1^0, \tilde\chi_1^0\to Z\tilde G$ (though it seems to me like something as simple as a vector-like quark could also work). Anyway, after typical preselection and requiring two OSSF leptons (if more than two are present they take the leading leptons), they define the on-Z signal region as: $$81< m_{l^+l^-}/\text{GeV}<101, \\ n_{jets}\ge2, \\ E_T^{miss}>225\text{ GeV,} \\ H_T>600\text{ GeV,} \\ \Delta\phi(jet_{12},E_T^{miss}>0.4,$$where $H_T$ is the scalar sum of the jet and lepton $p_T$ in the event, and the $\Delta\phi$ cut is designed to reject background from mismeasured jets faking large $E_T^{miss}$. And backgrounds are tough... $Z/\gamma^*+jets$ with mismeasured jets producing difficult-to-model instrumental $E_T^{miss}$ is potentially worrisome, but it is made negligible by the $\Delta\phi$ cut. Flavour-symmetric backgrounds (with a truth-level flavour ratio $ee:\mu\mu:e\mu$ of 1:1:2) from $t\bar{t}$, $WW$, single top, and $Z\to\tau\tau$ are dominant; they are estimated with a data-driven method using opposite-flavour data as a control region. Fake leptons are estimated from data.  Diboson, $t\bar{t}V$, $t\bar{t}VV$, and $t+Z$ are estimated from MC, making sure not to double count the flavour-symmetric component.
  
  The expected and observed number of events as a function of invariant mass in the dielectron and dimuon channels are shown below:
  
  
  
  
  For the sum of both channels the expected background is 10.6±3.2 with 29 events observed, which ends up corresponding to a 3.0σ excess.
  
  Now, CMS did a similar search in the on-Z SR in their paper and didn't see anything. So are the results consistent? It's possible. The CMS SR wasn't quite as tight as the one employed by ATLAS. After similar preselection, for an on-Z signal region defined as $$81< m_{l^+l^-}/\text{GeV}<101, \\ n_{jets}\ge2, \\ E_T^{miss}>200\text{ GeV,}$$CMS have an expected background of $\approx$ 87.3±12.1 with 72 events observed. So who knows, maybe if CMS demanded $H_T>600$ GeV they would see something too, or maybe not... 

• The biggest news of the week comes from Tuesday's astro-ph listings. This is not my area, so I can't comment intelligently, but anyone can read an abstract and look at Figures, so I will just sum up here for completeness and convenience (click the figures to make them larger)...
  
  1. Fermi-LAT released their Pass 8 constraints on dark matter annihilation (already largely known from preliminary results). They rule out dark matter masses $\lesssim 100$ GeV for a thermal relic annihilating to $b\bar{b}$ or $\tau\tau$. Those results are cutting into the best fit regions for the galactic centre excess.
  
  
  
  
  2. The Dark Energy Survey (DES) Collaboration has located eight new dwarf satellite galaxy candidates (of the Milky Way and/or Magellanic Clouds), and an independent Cambridge group has located nine using the publicly released DES deep photometry data. You can read the press release here.
  
  
  
  
  
  
  
  
  3. The new satellite candidates are prime spots to look for dark matter annihilation... so Fermi-LAT went and did it already! Assuming that the new candidates are dwarf spheroidals, they set a limit on the annihilation cross-section that rivals their Pass 8 results with known dwarfs above.
  
  
  
  
  4. But the story isn't over yet, because an independent group (which includes the Cambridge group that found nine candidates) has reported a gamma-ray excess, consistent with DM annihilation, in one of the new dwarf candidates. [Edit: The candidate is Reticulum II or DES J0335.6−5403, the green line in the above Fermi-LAT plot, which appears by eye to be the only line of all the candidates to have a weakened limit in the 10−few×100 GeV DM mass region, the region that would produce the excess.]
  
  
  
  
  And the dark matter annihilation saga continues...

• Protons bunches half-circled the LHC beam pipe last weekend for the first time since the long shutdown began! Injector tests sent bunches from the SPS into the LHC ring and through ALICE and LHCb on their way to beam dumps. Both ALICE and LHCb recorded splash events when the beam was made to collide with a target.
  
  
  
  
  You can play with the LHCb event here. First fully circulating beam is expected at the end of the month.

• PRL has published the Planck/BICEP2/Keck joint analysis, along with a Viewpoint article which tells some of the story -- we are reminded of the following: "... alternative models may be detectable with the next generation of experiments, some of which claim a sensitivity to r as small as 0.01. The competition is fierce, with at least six funded ground-based experiments underway (including the third version of BICEP), several balloon-borne experiments, and a number of proposed space missions."

• There's a nice feature at ScienceNews about the AMS experiment, the positron excess, and Samuel Ting; on the (unreleased) preliminary antiproton data he remarks: "intriguing".

• In video/audio media:
• CERN held their LHC Restart press conference earlier today. [50 minutes]
• LHC long shutdown preparations from CERN. [5 minutes]
• Animated video from symmetry magazine on $E=mc^2$. [2½ minutes]
• Ken Ribet on the bridges to Fermat's last theorem on Numberphile. [28 minutes]
• Tom Scott on numbers and linguistics: a discussion which spans counties, countries, continents and the far reaches of space on Numberphile. [9 minutes]
• Conversations with an Astrophysicist: Katie Mack and Scott Lewis on gravitational lensing. [36 minutes]
• More interesting science going on in Geneva: how chameleons change colour. [5 minutes]

• This month we are celebrating 100 years of general relativity. Science has a whole issue dedicated to the topic, with e.g. a nice review article here.

• Published in Nature yesterday, the Cassini orbiter has detected tiny rock grains emitted from the plumes of the Saturnian moon Enceladus, hinting at a subsurface ocean. You can read the articles at NASA, ESA, or Scientific American. Meanwhile a team using Hubble have used observations of aurora to indirectly suggest that there is a subsurface ocean on Ganymede, Jupiter's largest moon. Nice to see that there are complementary ways to measure these things.

• Today Rosetta is trying to listen for a signal from the Philae lander on Comet 67P/Churyumov-Gerasimenko. ESA released a cartoon video about it a few days ago [3 minutes]. The Lander Project Manager says, "It will probably still be too cold for the lander to wake up, but it is worth trying."

• Dawn went into orbit around Ceres successfully last Friday. Science begins in late April.
  

  Confirmed: I am in orbit around #Ceres http://t.co/BeOfCBefeM pic.twitter.com/b8FIZ8kZiK
  — NASA's Dawn Mission (@NASA_Dawn) March 6, 2015

Friday wrap-up: Higgs LFV decays, Higgs width, dissipative DM and rotation curves...

Wherein I list some (mostly) recent happenings, ramble a bit, and provide links, in an order roughly determined by importance and relevance to particle physics. Views are my own. Content very definitely skewed by my own leanings and by papers getting coverage, and it may not even be correct. It is a blog after all...

• CMS has submitted their paper on the search for LFV Higgs decays. This analysis supersedes the PAS from July (which has 20 citations). They see an excess of 2.4σ, which I wouldn't make much of, but it is worth keeping track of these "hints" because they motivate papers you see popping up on hep-ph. The following is a quick summary...
  
  They search in the $\mu\tau$ channel, which is experimentally the best channel in which you might hope to see something after taking into account bounds from LFV transitions. The best fit branching ratio for the excess corresponds to $Br(H\to \mu\tau)=0.84\%$, an order of magnitude below bounds from $\tau\to\mu\gamma$. The dominant backgrounds for the search are $Z\to\tau\tau$, $W+jets$, QCD multijets, and $t\bar{t}$. The latter three are certainlysome of the nastiest backgrounds around at the LHC. $W+jets$ in particular is responsible for a number of historical anomalies (see Tomasso's blog or his talk). Happily they can be estimated with the help of data in background-enriched regions, which is nice, but shape uncertainties must then be carefully considered as systematics. Anyway, let us move on to the results...
  
  
  
  
  

  The left and right columns correspond to the leptonic and hadronic $\tau$ decay channels respectively, and each row corresponds to an increasing number of jets (the last row is enhanced with VBF events). The variable they plot against is the collinear mass $M_{col}$, an estimator for the Higgs mass (in the signal events) constructed by assuming the neutrino (coming from the $\tau$ decay) momentum is equal to the projection of the missing momentum vector onto the direction of the $\tau$ decay products. The distributions driving the excess are $\mu\tau_e\;0$-jet, $\mu\tau_e\;1$-jet, and $\mu\tau_h\;2$-jet. That can be seen by eye above and in the branching fits themselves:
  
  

  

  
  
  One would assume (or hope?) that the ATLAS analysis is underway, and certainly it will be interesting to find out what they see.

• ATLAS has bounded the Higgs width at < 22.7 MeV at 95% CL (SM is 4.1 MeV) using the off-shell $gg\to VV$ Higgs boson signal, with assumptions (see below)! This supersedes their Conf Note from July and adds the WW channel to the analysis. The idea of doing this measurement (as far as I know) is based on the paper from Caola/Melnikov (1307). CMS managed to do the analysis and present it as a prepublication within 6 months of that paper (a phenomenal effort), rushed out for Moriond [pdf], and later published (in September) a bound of < 22 MeV at 95% CL [it should be noted that in the present ATLAS analysis the CLs method has been used which weakens their upper bound in the presence of the observed downward fluctuation of the low-statistics background; CMS used the regular $-2\ln L<4$ method and if ATLAS had done the same, judging by their Figure 12, their bound would rather be < 16.4 MeV]. The CMS result was presented as having "mild model-dependence," but not long after the bound was shown to be invalid for general new physics scenarios without some specific assumptions (see e.g. Englert/Spannowsky 1405). ATLAS appear to have specified clearly the assumptions going into their analysis...
  
  The ratio of the off-shell to on-shell g-g fusion signal strength is $$\frac{\mu_{\text{off-shell}}(\hat{s})}{\mu_{\text{on-shell}}}=\frac{\kappa^2_{g,\text{off-shell}}(\hat{s})\kappa^2_{V,\text{off-shell}}(\hat{s})}{\kappa^2_{g,\text{on-shell}}\kappa^2_{V,\text{on-shell}}}\frac{\Gamma_H}{\Gamma_H^{SM}},$$where the $\kappa$ are coupling scale factors of the Higgs to $gg$ and $VV$. The approximation CMS made was that the ratio of $\kappa$'s was equal to unity. ATLAS sets their limit under the assumption $$\kappa_{g,\text{on-shell}}^2\kappa_{V,\text{on-shell}}^2\le \kappa_{g,\text{off-shell}}^2\kappa_{V,\text{off-shell}}^2 .$$They also assume that none of any new physics which might alter the Higgs width changes substantially the background (of particular interest in this case since the off-shell signal and continuum background destructively interfere). The higher-order QCD corrections for the continuum background are not available, so in presenting their results they allow this K-factor to vary by a factor of 2 around that calculated for the SM Higgs.
  
  I find this measurement interesting as an independent way to probe the Higgs width. In principle it is possible to increase the Higgs width to > 22 MeV and have it consistent with all measurements, but it involves scaling up SM couplings while adding a new decay mode to keep the production×decay rate fixed. The global Higgs fit means that the upper bound on the Higgs branching to unobserved (not necessarily invisible) decays is < 21% for an otherwise SM Higgs. 

• An arXiv preprint has shown that a one-parameter generic dissipative dark matter model with supernovae heat source can explain the 'wiggles' in rotation curve data. Assuming that DM cooling is balanced by this heating mechanism and the DM density is in a stable state, it is shown that the density of DM is related to the supernovae formation rate in the disk. If the SN rate is related to the gas density via a Kennicutt-Schmidt law, then the DM density is connected to the baryonic gas density in the disk: $$\rho(r,\theta)=\tilde\lambda \int d\tilde\phi \int d\tilde r \tilde r \frac{[\Sigma_{gas}(\tilde r)]^N}{4\pi[r^2+\tilde r^2-2 r \tilde r \sin\theta\cos\tilde\phi]},$$where $N\approx 2$, and $\tilde\lambda$ is an appropriately averaged quantity which depends on the cross section, supernovae dark photon energy spectrum etc.
  
  You can now go out and apply this equation to gas density measurements and predict the rotation curve up to the constant $\tilde\lambda$. This was done for the spiral galaxy NGC1560 (below):
  
  
  
  
  

  There are more examples in the paper, fitting to dwarf galaxies from the LITTLE THINGS survey released last month. Reasonably good fits are obtained, especially considering it is only a one-parameter model; the best fit values of $\tilde\lambda$ vary only within a factor of two.

• The PICO-2L C3F8 Bubble Chamber in SNOLAB have reported the most sensitive direct detection constraints on WIMP-proton spin-dependent scattering to date. Below is a plot which compares various limits.
  
  
  
  
  
  The limits which appear to "beat" PICO-2L come along with some assumptions: IceCube, ANTARES, and SuperK are neutrino telescopes looking for annihilating dark matter in the sun; CMS/ATLAS search for mono-X signatures and assume an effective field theory (valid if the mediator mass is $\gg\sqrt{\hat{s}}$). In the conclusion they claim "These limits represent... the first time supersymmetric parameter space has been probed by direct detection in the SD-proton channel." Can't help but doubt this...

• The Neutrino Telescopes conference (NeuTel XVI) is well under way and is keeping a blog here which contains summaries of talks and posters. I really like this method for gathering in one place succinctly and accessibly the important information; of course one can still access the full talks to find out more.
  
  Here is one interesting post from Francesco Iachello. He claims that quoted neutrinoless double beta decay bounds are too strong by a factor 2.5--6 due to the overestimate of a nuclear matrix element factor. This would mean that the inverted hierarchy region still allowed by Planck cannot be probed by $0\nu2\beta$ experiments in near future.

• There is an interview with Jamie Bock of the BICEP2 experiment at Sean Carroll's blog. Here is an excerpt on the decision to release results when they did: The question really is, should we have waited until better data were available on galactic dust? Personally, I think we did the right thing. The field needed to be able to react to our data and test the results independently, as we did in our collaboration with Planck. This process hasn’t ended; it will continue with new data. Also, the searches for inflationary gravitational waves are influenced by these findings, and it is clear that all of the experiments in the field need to focus more resources on measuring the galaxy.

• Twenty years ago on Tuesday was the discovery of the top quark at Tevatron. The papers of CDF and D0 were released together and can be read for free at PRL Milestones. Top at Twenty at Fermilab is celebrating this milestone from 9-10 April, in the traditional way of particle physicists: talks! Reviews of fundamental measurements of the top quark, measurements of top quark production and decay, theoretical talks on how the top quark fits into the Standard Model and its potential extensions, etc...

• I don't know how significant this tweet from today is, but perhaps something to be aware of... [Edit: never mind, must have been minor (see second tweet)]
  

  #LHC 17:25:50 Major failure in the Proton source. No beam tonight. Shots on T12&T18 TEDs cancelled for tonight. :( pic.twitter.com/byHWLiPnrJ
  — Andrew Elwell (@lhcstatus) March 5, 2015

  [1/2] #LHC 13:58:05 Source repaired. protons back. DSO test onigoing. Time estimated for sector test start up 15:30. pic.twitter.com/o7yajtaiBW
  — Andrew Elwell (@lhcstatus) March 6, 2015

  
  

• In video/audio media:
• Based on excerpts from the book This Idea Must Die, Sean Carroll and Seth Lloyd talk about scientific ideas which they think must die: the universe and falsifiability. [17 minutes]
• An interview with Gerard t’Hooft. [10 minutes]
• Destination Dwarf Planet and Dawn Nears Ceres from NASA JPL, including the manoeuvre that will bring Dawn into orbit today. [3 and 2 minutes]

• A paper published yesterday in Science has measured the D/H enrichment of atmospheric water on Mars. They found a D/H value enriched by a factor of about 7 relative to Earth’s ocean, which indicates that Mars has lost most of its water to space -- about six times the amount presently locked up in the Martian ice caps. This implies that Mars once had an ocean covering 20% of the planet's surface, up to one mile deep, and was wet for >1.5 billion years. Plenty of time for life! There's a 4 minute video about it from NASA Goddard, or an article at the guardian if you prefer.

• Another paper in Science reports the observation of a gravitationally lensed supernova forming an Einstein cross. Because of the different travel times for light rays taking different paths around the lensing cluster, it is suspected that the supernova explosion would have appeared before (1964 and 1995) in another part of the sky, and will appear again elsewhere some time before 2020. There's an NY Times article here with a video.

• Here is Rolf Heuer on the European Commission's decision to divert €2.7 billion (4%) of the EU’s science funding programme, Horizon 2020, to alternative investments.

• Not sure what to think of the following tweet from Murdoch, but with The Australian's recent flip-flopping on Abbott who knows...
  

  Ok, call it climate change. Can we have honest debate, and if true how bad and how much fault of humans?
  — Rupert Murdoch (@rupertmurdoch) February 27, 2015

• If you aren't already following Sabine Hossenfelder blogging at BackReaction, you should. Two more interesting pieces from her this week: 1) Are pop star scientists bad for science? 2) Can we prove the quantization of gravity with the Casimir effect? Probably not.

• A list of pioneering women of physics from the Perimeter Institute.

• Very many articles knocking around this week about Homer Simpson predicting the Higgs boson mass, apparently relating to Simon Singh's new(ish) book on Mathematics and The Simpsons. Actually, you can now read that chapter for free here.
  
  
  
  
  

  If you actually calculate it you find it to be $\approx 775$ GeV. Not so miraculous. Change the $\pi$ to a $\frac12$ and he does a lot better, but since we know that the Higgs mass is just a conspiracy of gravity, QCD, and the weak force, maybe he should have guessed $$ \approx \pi\left(\frac{m_p}{2m_W}\right)^8\sqrt{\frac{hc}{G}}, $$ at tree level of course.

• Lastly, images from space...
• Some shots from Rosetta: all-round activity and and image of its own shadow captured during the recent comet flyby!
  
  
  
  
  
  
  
  
• Dawn is approaching Ceres. It should go into orbit some time today! See the video section above to look at the manoeuvre that will get it there.
  

  A full #Ceres rotation and more as Dawn prepares to make history http://t.co/oZedzklMvv #space pic.twitter.com/ycMvpzphZm
  — NASA's Dawn Mission (@NASA_Dawn) March 2, 2015

Friday wrap-up: dark matter direct detection in Australia, ICARUS vs MiniBooNE...

This week I have been at the CoEPP Annual Workshop on Australia's exclamation point. Highlights have included new results on the CKM unitarity triangle (Pesantez/Kandinsky) and the art installation about viXra. But actually, perhaps the most exciting thing is the update on the southern hemisphere underground lab, which is my first point...

• The possibility of a direct dark matter detection experiment in Australia is increasing! The Victorian government has pledged $1.75 million to Stage 1 of the Stawell Underground Physics Laboratory and is seeking matching funds from the Commonwealth. This comes after a three-day workshop near Stawell (a few hours from Melbourne) in October last year with INFN representatives to discuss the possibility of collaborative research. The response from the Stawell community has been welcoming.
  
  In Hobart we heard an update on geological backgrounds. In short: neutron flux okay, gamma flux okay, radon flux high but manageable with surface air / adsorption on activated carbon / shielding. All good news.
  
  A detector in the southern hemisphere has the capacity to settle the case for the DAMA/LIBRA annual modulation signal. If the DAMA/LIBRA signal is real and originates from Earth's traverse through the dark matter halo, then the signal should not change for a similar experiment in the southern hemisphere. If the signal is spurious, due to some local Gran Sasso background or an unaccounted seasonal effect, then the signal will disappear or swap phase. A diurnal modulation signal might even be observed if dark matter is captured within the Earth. Any result would be an interesting result, and a new generation twin experiment would be particularly interesting.
  
  Professors Elisabetta Barberio and Geoff Taylor appeared on 936 ABC Radio Hobart and talked about it.

• Related is a Wall Street Journal article about direct detection at Gran Sasso, specifically the Darkside-50 experiment. It includes a two minute video. 

• ICARUS has updated and revised their comparison to the MiniBooNE $\nu_\mu$-$\nu_e$ oscillation anomaly, still suggesting an "unexplained nature or an otherwise instrumental effect for the MiniBooNE low energy event excess." The paper is worth reading if only for the maligning undertones... ICARUS already presented their results in July 2013 which appeared to rule out MiniBooNE at >99% CL:
  
  
  
  
  
  MiniBooNE posted a critical reply which "explains and corrects the mistaken analysis published by the ICARUS collaboration." The confusion seems to be in the translation between the reconstructed energy $E^{QE}_\nu$ and $E_{True}$. Let me quote an excerpt from the new ICARUS paper to give you a feel for their thoughts on the issue:
  
  It appears that the reconstructed energy is affected by a huge non-Gaussian smearing compared with the true neutrino energy, as clearly stated in [the MiniBooNE reply] (see Figure 2), in contrast with the much better 11% resolution on $\nu_e$ event energy quoted in a previous paper. This difference between $E_{True}$ and $E^{QE}_\nu$, for which MiniBooNE gave a quite elliptical explanation, is the major cause of the problem in using the L/E (or E/L) to compare data with expectations...
  
  They make two further remarks. First they argue that the MiniBooNE reply implies that MiniBooNE's own results were represented in a misleading way in the original paper, by being directly compared to LSND data. Second they point out that the MiniBooNE quoted errors are inconsistent from paper to paper, and they even have a plot comparing the errors to make the point.
  
  
  Anyway, upon updating the comparison, the MiniBooNE anomaly appears excluded at 90% CL but no longer at 99% CL.

• LHC restart is expected in the last week of March:
  

  Expecting to #RestartLHC last week of March, says Director of Accelerators at Press Briefing @AAASmeetings. VNR #LHC https://t.co/FbVdwkqlB6
  — CERNpressoffice (@CERNpressoffice) February 15, 2015

• The LHC PR machine has really started to gear up. Checking the In the News section at Interactions.org I count 26 news articles in the last week. It's the usual sell: the big bang, Higgs, SUSY, dark matter, and baryogenesis.

• The proton-electron mass ratio was the same 12 billion years ago as it is now.

• Old news, but I just learned that since the end of September last year you can search for papers in inspire by just copy-pasting a reference from a paper and using: find rawref "..." . That will save us a bit of time.

• Here is a discussion with George Efstathiou (Kavli Institute, Planck) on Planck and inflation, quantum gravity, younger first stars, dark matter, primordial gravitational waves...

• Related, the Planckoscope got a sychrotron polarisation layer last weekend.

• Natalie Wolchover at Quanta magazine always produces well-written and well-balanced articles (even Luboš agrees), and has delivered another one, this time on string theory; the byline asks, "Researchers are demonstrating that, in certain contexts, string theory is the only consistent theory of quantum gravity. Might this make it true?"

• There's more in the press on falsifiability, Carroll's call for its retirement, the Ellis and Silk comment, Tegmark's multiverse hierarchy, Dawid's post-empiricism etc. Frank Wilczek threw his hat into the ring: "I think falsifiability is not a perfect criterion, but it’s much less pernicious than what’s being served up by the ‘post-empirical’ faction. Falsifiability is too impatient, in some sense... It’s an important discipline, but if it is applied too rigorously and too early, it can be stifling."
  

  I get quoted, on falsifiability: http://t.co/oz2e7xRGgS Not often I refer to a "pernicious" "faction", but appropriate here.
  — Frank Wilczek (@FrankWilczek) February 12, 2015

• On the topic of Frank Wilczek, he has launched a mysterious web site for "Wolfcub Vision Inc".

• On the arXiv now are two papers on the science, mathematics, and computation behind the black hole and wormhole visualisations in "\emph{Interstellar}".

• There is a new book out from Smolin, and also a biography on Bruno Pontecorvo. For reviews on the former see Woit or the guardian, for the latter there is a review by Freeman Dyson behind a paywall.

• It appears that Lisa Randall will be releasing a book "Dark Matter and the Dinosaurs" at the end of October this year. If you're wondering about the connection, Randall has an arXiv paper which links comet impacts to periodic transits of the Oort cloud through the galactic disk, hypothesised to align with a dark matter disk (if some component of dark matter is dissipative). Actually, The Economist picked up this story yesterday, though there's no mention of Randall. 

• If we're worried about that, maybe we should also worry about the star that passed through the cloud only 70,000 years ago according to research published last week.

• In video media...
• Ray Volkas public lecture, "The Known Unknowns of the Universe," at University of Tasmania. [1 hour]
• Sixty Symbols interviewed Clare Burrage (University of Nottingham) for a video on axions and the light shining through walls experiment [6 minutes]. There's also some bonus footage here [3 minutes].
• CERN released a video of some of the beam pipe upgrades performed during the long shutdown (with funky tunes) [3 minutes]. There's also a (less funky) partner article on the upgrades.
• ESA video on Rosetta's closest approach on 14 Feb. [4 minutes]
• An interview with Scott Aaronson (MIT professor, theoretical computer scientist, and blogger at Shtetl-Optimized) on QM, P=NP, ...
• Conversations with an Astrophysicist on Fast Radio Bursts with Scott Lewis, Katie Mack, and Emily Petroff. [44 minutes]
• How to construct a 17-gon at Numberphile, as first proven by Gauss. [13 minutes]

• There's a nice article at Washington Post on why science is hard to believe.

• Doing the rounds: Does science produce too many PhD graduates?

• There is an online petition circulating to adopt the term "climate denier" in lieu of the term "climate skeptic". The New York Times has a story. Meanwhile the Australian Academy of Science has released a 32 page booklet on climate change to dispel confusion and misinformation.

• The Pale Blue Dot photograph taken by Voyager 1 is 25 years old. Read the famous reflections by Sagan here. Voyager 1 entered interstellar space in mid-2012; it's still sending back data, but by 2030 will be unable to power any instrument. Click here to see where it is now.

• Lastly, images from space...
• Mysterious plumes are erupting on Mars (gif here) and as Dawn edges closer, the nature of the white spots on Ceres are still unknown: "We expected to be surprised; we did not expect to be this puzzled"; it will be in orbit on March 6. Are we living at the beginning of a sci-fi novel?
  
  
  

• New Horizons is approaching Pluto and has imaged its moons Nix and Hydra (within diamonds):
  
  
  
• New closeup of Comet 67P/Churyumov-Gerasimenko from Rosetta's flyby:
  
  
  
  
  
• Hubble has imaged a galactic merger:
  
  
  
  
  
• Comet Lovejoy and its tail in the solar wind:
  
  
  

Friday wrap-up: Planck, long-lived particles, dark matter, neutrinos...

Wherein I list some (mostly) recent happenings, ramble a bit, and provide links, in an order roughly determined by importance and relevance to particle physics.

• Word from our Prime Minister is that good government started on Monday! Now we can forget about our science funding problems and just get on with it. So let's get on with it...

• From last week, there is more on the Planck+BICEP2+Keck result from Matt Strassler and from Sean Carroll, in order of readability for the layman. And here is a nice popular science article from Ars Technica.

• As for the rest 2015 Planck release, the base cosmological parameters have hardly changed (see e.g. Table 1 of this paper). ΛCDM of course continues to explain everything extremely well. The $\Sigma m_\nu$ upper limit is down to 0.17 eV (Planck TT, TE, EE+lowP+BAO) at best, almost at a level to rule out an inverted hierarchy ($\Sigma m_\nu\gtrsim 0.1$ eV). $N_{eff}$ is still at 3.04 ± 0.18 (Planck TT, TE, EE+lowP+BAO), consistent with the standard value 3.046. There is no longer a hint of an excess there. As for inflation, Jester weighed in, and Planck present their results in this paper:
  
  
  Looks like the canonical Starobinsky $R^2$ inflation (1980) is taking the lead, but time will tell... experiments will need to probe at the level r~0.001 to test it.

• The resemblance between Van Gogh and Planck has not gone unnoticed:
  
  
  

• At least LHCb are finding new particles! "Observation of Two New $\Xi^-_b$ Baryon Resonances" was just published with a write-up in APS Physics Spotlights. There's also a Scientific American article.

• BaBar released a new paper, "Search for Long-Lived Particles in e+e− Collisions". No significant signal is observed. It seems worth mentioning that they see a high local significance of events in the dimuon mode at $m_{\mu\mu}\approx 212$ MeV, which interestingly is very close to the HyperCP anomaly, but they say it is consistent with background from photon conversions. Anyway, from the point of view of a phenomenologist I especially like the effort BaBar has put into presenting their results in a model independent way. For example:
  
  1. They provide upper limits on $\sigma(e^+e^-\to LX)\mathcal{B}(L\to f)\epsilon(f)$, where $L$ is the long-lived particle and $f$ is the final state, which are completely agnostic of the production mechanism.
  2. They provide limits on $\mathcal{B}(B\to LX_s)\mathcal{B}(L\to f)$ where $X_s$ is "strange stuff", which reduces significantly some theoretical uncertainties for exotic $B$ decays and increases the possible signal yield.
  3. They look at six different two-body final states.
  4. On top of this, they will provide the full efficiency as a function of $m$, $c\tau$ and $p_T$ in supplementary material, so that their results can be reinterpreted.
  
  Very well done from BaBar. Their measurement has implications for a very simple extension of the Standard Model with a real singlet scalar mixing with the Higgs (a Higgs portal). I have quickly reinterpreted their Fig. 3 bounds (1 cm < $c\tau_L$ < 100 cm) on the $\mu^+\mu^-$, $\pi^+\pi^-$ and $K^+K^-$ final states, assuming the limit lines are $\mathcal{B}(B\to LX_s)\mathcal{B}(L\to f)\lesssim 10^{-6.5}$...
  
  
  
  
  
  The above plot shows exclusions (within solid lines) for the model as a function of light scalar mass and mixing (see a previous paper of ours). The incremental shadings represent different lifetime regions and the shaded region between 0.28 GeV and 4 GeV masses indicates a very uncertain region for branching predictions; between we choose the most recent calculation (still >20 years old!) below 1.4 GeV and a perturbative calculation above. The approximate exclusion from BaBar is shown as the purple dashed line. Indeed they are exploring previously unexplored parameter space of interest for an inflationary model of Bezrukov/Gorbunov (between black dashed lines). They are limited by difficult backgrounds between 0.37 GeV and 0.86 GeV masses. The purple dotted line indicates the region they would have excluded if they could limit $\mu^+\mu^-$ and $\pi^+\pi^-$ final states to the same level in that region. I am interested to get my hands on the supplementary material when it is released.

• A new paper published in Nature Physics (not on the arXiv [edit: now it is]) this week is doing the rounds; it infers that there must be dark matter in the inner region (within the solar circle) of our own galaxy. It's behind a paywall, but there is a press release here. The main plot is below.
  
                    
  
  The authors have compiled an exhaustive list of rotation curve measurements (red), as well as gathered a set of models for the baryonic contribution from which they form their "baryonic bracket" (grey). The lower panel shows that all baryonic-only models are already ruled out at 5-sigma by the time we arrive at our galactic radii. Hence there must be a dark matter component in the inner Milky Way. They do not appeal to any dark matter density profile, so in that sense it is a model-independent result (but of course it is not independent of the baryonic models!). Nevertheless you can see that a typical Navarro-Frenk-White profile models the residuals extremely well. This is nice to know.
  
  It is interesting that you can already infer dark matter just with measurements of the rotation curve within the solar circle, and I suppose the result may also be useful to constrain dark matter distributions of interest to direct and indirect detection. I do not think it is "the first observational proof of the presence of dark matter in the innermost part of the Milky Way" as the press release claims (the paper does not claim this). It is obvious that you need some dark matter component in the Milky Way to explain the rotation curve measurements at large galactic radii, and nobody thinks that all that dark matter is accumulated beyond 8 kpc! Those measurements are already observational evidence for dark matter in the inner Milky Way. Regardless, Hooper et al. already saw dark matter at the galactic centre...

• IceCube have released their results on the flavour ratio of astrophysical neutrinos above 35 TeV. They release a very nice plot which fits the observed flavour ratio at Earth:
  
  
  
  
  Averaging neutrino oscillations over astronomical distances would give a value in the blue triangle for any flavour ratio at the source. The blue circle $\approx(1:1:1)_{Earth}$ marks the expected value for pion decays as the dominant source. Any measurement inconsistent with the (very thin) blue triangle would be a signal of new neutrino physics, such as neutrino decay, sterile neutrinos, or CPT violation (see for example here and here). Tommasso discusses it a little more here. [Edit: there is a short article at the IceCube web site also.]

• If you'd like to read some more on the "Firewall Phenomenology with Astrophysical Neutrinos" paper that appeared on hep-ph last week, Bee at Backreaction has written a nice summary. The paper shows that IceCube's PeV neutrinos could be explained by a suitable emission spectra from black hole firewalls.

• CMS is alive! Magnet comes on next week.
  

  ITS ALIVE MUHAHAHA (@CMSexperiment that is) Cosmic muon being events deftly collected now by Dr Rebeca G-Z et al pic.twitter.com/qlQnSuxqnB
  — Freya Blekman (@freyablekman) February 11, 2015

• Physicist Val Fitch, whose discovery (along with James Cronin) of CP violation in a 1964 experiment won him the 1980 Nobel Prize, has died at the age of 91. Read about his life and contributions here.

• Steven Weinberg has written a history book, released a few weeks ago. According to the About, "To Explain the World is a sweeping, ambitious account of how difficult it was to discover the goals and methods of modern science, and the impact of this discovery on human knowledge and development." For some reason it even garnered praise from Ian McEwan.

• IPMU has recently published a 26 page transcript [pdf] of a conversation with Edward Witten after he was awarded a Kyoto Prize last year for "Outstanding Contributions to the Development of Mathematical Sciences through the Exploration of Superstring Theory". Peter Woit highlights some excerpts and talks about it on his blog.

• In video media... 
• Big Bang Theory made an episode based on a post at Quantum Diaries. There's a little Q&A about it at symmetry magazine, and you can read Ken Bloom's story here and see the traffic it brought to Quantum Diaries.
• Sean Carroll responding to the fine-tuning argument for God. [9 minutes]
• Veritasium interviews Chris Hadfield about what it's like to see the Earth from space and comments on climate change. [4 minutes]
• NASA released a five year timelapse of the Sun from the Solar Dynamics Observatory. [3 minutes]
• Winner of the Bad Ad-Hoc Hypotheses Festival (BAHFest) - Sarah Hird: Why do Mammals Sleep? [7 minutes]
• Numberphile on the superellipse (Lamé curve) and architectural design. [7 minutes]
• A moderately sized meteor (~0.5m) created a fireball (bolide) above New Zealand on Wednesday and was captured on dashcam. You can read about bolides here, with graphs! If you want to see what a bigger one can do, try the Chelyabinsk event from two years ago, perhaps the biggest meteor to enter the atmosphere since Tunguska (1908).

• This blog post has a gif showing the history of planet detection in 1 minute, and the exoplanet gold rush starting at the year ~2000, with some discussion. Here's where we were by the end of last year:
  
  
  

• If you have a brief idea, why not consider submitting to the newly created Journal of Brief Ideas? Citable ideas in 200 words or less! There's a Brief Article at nature about it.

• On fake academic journals and "Rogeting".

• Are you ready for Run II? Take the LHC Quiz!

• SpaceX launched the Deep Space Climate Observatory (DSCOVR) on Wednesday. You can watch the launch and read a little about it at space.com. DSCOVR will sit at the L1 Lagrange point between the Earth and the Sun, observe the climate, and serve as an early alert "buoy" for geomagnetic storms. The satellite is the resurrection of a previous project championed by Al Gore; he wrote, "DSCOVR has embarked on its mission to further our understanding of Earth and enable citizens and scientists alike to better understand the reality of the climate crisis and envision its solutions. DSCOVR will also give us a wonderful opportunity to see the beauty and fragility of our planet and, in doing so, remind us of the duty to protect our only home."

• There is a little more on the proposed NASA Europa Clipper mission at The Conversation.

• Finishing up with some photos from space for the week:
• Rosetta took an incredible shot of its comet. Tomorrow it will make its closest approach yet at 6 km above the surface, the Sun at its back.
  
  
  

• Below is the Curiosity rover as pictured by NASA's Mars Reconnaissance Orbiter:
  
  
  

• Lastly, here is an image of galaxies SDSSCGB 8842.3 and SDSSCGB 8842.4 as pictured by Hubble and released on Monday 
  
  
  

Friday wrap-up: Planck, HESS, exoplanets...

• Today Planck has released a statement [edit: web site has been hidden, but luckily the internet keeps backups] [edit 2: paper is now available from here] about the combination analysis of BICEP2+KECK+Planck re: primordial gravitational waves. Be sure to click the "Expert" version for some plots. (English speakers try google translate). The bottom line is no significant non-zero measurement, with the tensor-to-scalar ratio r<0.13 at 95% C.L. It could just be dust.
  
  No doubt we will hear more about it in the coming week(s).

• H.E.S.S. has discovered a trio of extremely luminous gamma-ray sources in the Large Magellanic Cloud, "the first time that stellar-type gamma-ray sources are detected in an external galaxy, at these gamma-ray energies."
  

• Some incredible results coming out of the Kepler mission data. The survey has discovered >1000 exoplanets, with notable recent finds: an 11 billion year old star with Earth-sized planets; a planet with a ring system ~120 million kilometres in diameter, or almost the distance of the Earth to the Sun (see a video of the exoring model here), and; a star with three Earth-sized planets straddling the system's habitable zone.

• Richard Dawid's book "String Theory and the Scientific Method" and surrounding ideas of post-empirical science continues to cause waves within the blogosphere. The argument seems to be that String Theory is likely correct because: (a) there are few viable alternatives, (b) the more it is studied the more it appears to hold together coherently, and (c) it is the extrapolation of a previous programme of study (the Standard Model) which already succeeded. But without experiment to ground it in reality, is it science? We can go back to May for a couple of interesting book reviews from two opposing sides: Woit and Motl.

• Related is this NPR piece on the multiverse.

• Worth a look also are pieces on Helen Quinn at Symmetry Magazine, and Yitang Zhang (of bounded prime gaps fame) in the New Yorker.

• In other science news, images of Ceres are arriving from Dawn (what is the white spot?), the Rosetta comet mission is returning results, and fish live beneath 740 metres of ice in Antarctica.

• Lastly, AndromedaBot is a twitter account which tweets excerpts from Hubble's largest photo (of Andromeda) every half-hour.