he properties of these structures are consistent with their interpretation as four-quark particles, which are considered as "exotic", (hence the "exotic-like" name in the title), although the details of the four quark $c{\bar c}s{\bar s}$ binding mechanism is still under discussion.Read also paper 1 and paper 2
In the SM all charged leptons, such as taus ($\tau$) or muons ($\mu$), interact in an identical fashion (or, in physicists' language, have the same "couplings"). This property is called "lepton universality". However, differences in mass between the leptons must be accounted for, and affect decays involving these particles. The $\tau$ lepton is much heavier than the $\mu$ lepton and therefore the SM prediction for the ratio $R(D^*)$ is substantially smaller than 1. This ratio is considered to be precisely calculable thanks to the cancellation of uncertainties associated with the $B$ to $D^*$ meson transition.
The LHCb collaboration published in Nature Physics a paper based on run 1 data which reports the determination of the parameter $|V_{ub}|$ describing the transition of a $b$ quark to a $u$ quark. This measurement was made by studying a particular decay of the $\Lambda_b^0$ baryon. Other measurements of $|V_{ub}|$ by previous experiments had returned two sets of inconsistent results, depending on which method was used to determine the parameter. Theorists had suggested that this discrepancy could be explained by the presence a new particle contributing to the decay process, which affected the result differently, depending on the measurement method. Today's result from LHCb removes the need for this new particle, while the puzzle of why the original sets of measurements do not agree persists.
Once upon a time, there was a controversy in particle physics. There were some physicists who denied the existence of structures more elementary than hadrons, and searched for a self-consistent interpretation wherein all hadron states, stable or resonant, were equally elementary. Others, appalled by the teeming democracy of hadrons, insisted on the existence of a small number of fundamental constituents and a simple underlying force law. In terms of these more fundamental things, hadron spectroscopy should be qualitatively described and essentially understood just as are atomic and nuclear physics.(11)
Three quarks for Muster Mark!
Sure he has not got much of a bark
And sure any he has it's all beside the mark.
from Finnegan's Wake by James Joyce
Fabiola Gianotti is an Italian particle physicist, a former spokesperson of the ATLAS experiment at the Large Hadron Collider (LHC) at CERN in Switzerland, considered one of the world's biggest scientific experiments. She has been selected as the next Director-General of CERN, starting on 1 January 2016.She is the 4th italian particle physicist to became Director General at CERN after Amaldi (1952-1954), Rubbia (1989-1993) and Maiani (1999-2003).
This collection of 31 articles presents the initial scientific results extracted from this first Planck dataset, which measures the cosmic microwave background (CMB) with the highest accuracy to date. It provides major new advances in different domains of cosmology and astrophysics.In the first paper there is an overview of 2013 science results, and we can read:
The Universe observed by Planck is well-fit by a six parameter, vacuum-dominated, cold dark matter (ACDM) model, and we provide strong constraints on deviations from this model.But, in the meanwhile, ATLAS published a preprint about the quest of the dark matter in LHC:
The data are found to be consistent with the Standard Model expectations and limits are set on the mass scale of effective field theories that describe scalar and tensor interactions between dark matter and Standard Model particles. Limits on the dark-matter--nucleon cross-section for spin-independent and spin-dependent interactions are also provided. These limits are particularly strong for low-mass dark matter. Using a simplified model, constraints are set on the mass of dark matter and of a coloured mediator suitable to explain a possible signal of annihilating dark matter.Tommaso Dorigo, examining ATLAS' results, concludes:
the ATLAS search increases significantly the sensitivity with respect to past searches, but no signal is found. As attractive as DM existence is as an economical explanation of a wealth of cosmological observations, the nature of dark matter continues to remain unknown.
for their decisive contributions to the large project, which led to the discovery of the field particles W and Z, communicators of weak interactionThe story of this Nobel, however, began eight years earlier, in 1976. In that year, in fact, SPS, the Super Proton Synchrotron, begins to operate at CERN, originally designed to accelerate particles up to an energy of 300 GeV.
The same year David Cline, Carlo Rubbia and Peter McIntyre proposed transforming the SPS into a proton-antiproton collider, with proton and antiproton beams counter-rotating in the same beam pipe to collide head-on. This would yield centre-of-mass energies in the 500-700 GeV range(1).On the other hand antiprotons must be somehow collected. The corresponding beam was then
(...) stochastically cooled in the antiproton accumulator at 3.5 GeV, and this is where the expertise of Simon Van der Meer and coworkers played a decisive role(1).
CP-symmetry states that the laws of physics should be the same if a particle is interchanged with its antiparticle, and then its spatial coordinates are inverted.The CP violation is discovered in 1964 by Christenson, Cronin, Fitch, and Turlay (Cronin and Fitch awarded the Nobel Prize in 1980) studying the kaons' decays and it could have a key-role in the matter-antimatter imbalance.
LHComedy brings science-themed stand-up comedy to the Geneva area. Bringing our audience a mixture of laughs and insight, we bring our passion about science and technology to the world with our own stories and experiences of life at CERN.(more at lhcomedy.web.cern.ch)
According to Joaquim Matias from Universitat Autonoma de Barcelona and colleagues the deviation in $P_5'$ and small discrepancies in the other angular observables for this decay, follow a pattern. In a recent paper the authors claim that a global analysis of the LHCb data, together with previous measurements, show a deviation of $4.5 \sigma$ with respect to Standard Model expectations, which can be explained with the same mechanism. This demands further investigation, in particular to re-evaluate all the sources of theoretical uncertainty, and to understand the effects of correlations between the experimental measurements.(via LHCb)
is considered a very important process to investigate possible manifestation of new physics. This decay process is forbidden in the first approximation in the Standard Model (SM) of particle physics and moreover in the second-order processes that govern the process in the SM the emitted photon is expected to be strongly polarised. Therefore it is very sensitive to new physics effects arising from the exchange of new heavy particles in electroweak penguin diagrams (see 14 June 2013 news). Indeed, several models of new physics predict that the emitted photon should be less polarised than in the SM. Up to now different experiments have measured the decay rate of this process, ruling out significant deviations of the rate from the SM prediction and strongly reducing the allowed parameter space of new physics models. The photon polarisation was, however, never previously observed.I think that this is a really intriguing news for a particle physics point of view.
The data are in good agreement with the expected distributions of a $J^P=0^+$ particle while the graviton-inspired $J^P=2^+$ model, that is expected to be produced dominantly via the gluon fusion process, is excluded at more than 99.9% confidence level.We could say that it starting the elimination process of the models that would lead the research of the new physics beyond the Standard Model for the next years. A good luck to all of them, but we don't forget the key role of the Standard Model, that is in some sense confirmed by this last draft from ATLAS.
new physics and there are a great deal of models that can come with such a numberIn order to resolve the question (is the new boson the only Higgs' boson or simply a Higgs' boson?) we have to wait the end of the maintenance work of LHC, but in the meantime we could play with the Quark Matter Card Game, in particular the variant named Higgs Boson - on Your Own!
Object of the game: to win, by detecting a decay of a Higgs boson. If this does not happen in a given game, one can win by statistics, by collecting the largest number of particle cards.The proposed game is a variation of Memory
A search for the Standard Model Higgs boson in proton–proton collisions with the ATLAS detector at the LHC is presented. The datasets used correspond to integrated luminosities of approximately $4.8 \, fb^{−1}$ collected at $\sqrt{s} = 7$ TeV in 2011 and $5.8 \, fb^{−1}$ at $\sqrt{s} = 8$ TeV in 2012. Individual searches in the channels $H \rightarrow ZZ^{(*)} \rightarrow 4l$, $H \rightarrow \gamma \gamma$ and $H \rightarrow WW^{(*)} \rightarrow e \nu \mu \nu$ in the 8 TeV data are combined with previously published results of searches for $H \rightarrow ZZ^{(*)}$, $WW^{(*)}$, $b \bar{b}$ and $\tau^+ \tau^-$ in the 7 TeV data and results from improved analyses of the $H \rightarrow ZZ^{(*)} \rightarrow 4l$ and $H \rightarrow \gamma \gamma$ channels in the 7 TeV data. Clear evidence for the production of a neutral boson with a measured mass of 126.0 ± 0.4 (stat) ± 0.4 (sys) GeV is presented. This observation, which has a significance of 5.9 standard deviations, corresponding to a background fluctuation probability of 1.7 × 10−9, is compatible with the production and decay of the Standard Model Higgs boson.Aad, G., Abajyan, T., Abbott, B., Abdallah, J., Abdel Khalek, S., Abdelalim, A.A., Abdinov, O., Aben, R., Abi, B., Abolins, M. & (2012). Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC, Physics Letters B, 716 (1) 29. DOI: 10.1016/j.physletb.2012.08.020
Results are presented from searches for the standard model Higgs boson in proton–proton collisions at $\sqrt{s} =$ 7 and 8 TeV in the Compact Muon Solenoid experiment at the LHC, using data samples corresponding to integrated luminosities of up to $5.1 fb^{−1}$ at 7 TeV and $5.3 fb^{−1}$ at 8 TeV. The search is performed in five decay modes: $\gamma \gamma$, $ZZ$, $W^+ W^−$, $\tau^+ \tau^-$, and $b \bar{b}$. An excess of events is observed above the expected background, with a local significance of 5.0 standard deviations, at a mass near 125 GeV, signalling the production of a new particle. The expected significance for a standard model Higgs boson of that mass is 5.8 standard deviations. The excess is most significant in the two decay modes with the best mass resolution, $\gamma \gamma$ and $ZZ$; a fit to these signals gives a mass of 125.3 ± 0.4 (stat.) ± 0.5 (syst.) GeV. The decay to two photons indicates that the new particle is a boson with spin different from one.Chatrchyan, S., Khachatryan, V., Sirunyan, A.M., Tumasyan, A., Adam, W., Aguilo, E., Bergauer, T., Dragicevic, M., Erö, J., Fabjan, C. & (2012). Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC, Physics Letters B, 716 (1) 61. DOI: 10.1016/j.physletb.2012.08.021
Following recent ATLAS and CMS publications we interpret the results of their Higgs searches in terms of Standard Model operators. For a Higgs mass of 125 GeV we determine several Higgs couplings from 2011 data and extrapolate the results towards different scenarios of LHC running. Even though our analysis is limited by low statistics we already derive meaningful constraints on modified Higgs sectors.Klute, M., Lafaye, R., Plehn, T., Rauch, M. & Zerwas, D. (2012). Measuring Higgs Couplings from LHC Data, Physical Review Letters, 109 (10) DOI: 10.1103/PhysRevLett.109.101801 (arXiv)
I don't see any CERN related things here, so I want to mention how Linux (specifically, Scientific Linux and Ubuntu) had a vital role in the discovery of the new boson at CERN. We use it every day in our analyses, together with hosts of open software, such as ROOT, and it plays a major role in the running of our networks of computers (in the grid etc.) used for the intensive work in our calculations.If you want, you can download the distributions used at CERN at the page Linux @ CERN. The CERN distribution is a Scientific Linux (a distribution used also at Fermilab) rebuilded with the Red Hat. In general the Linux distributions are the most used in the scientific world, in particular in physics and mathematics, and the reasons are the same that the anonimous research writes in another comment:
Yesterday's extremely important discovery has given us new information about how reality works at a very fundamental level and this is one physicist throwing Linux some love.
In terms of data analysis, Windows could be used in principle. We could also use some type of device that manipulates symbols on a strip of tape according to a simple table of rules. Linux is used because it is most appropriate for the job. Linux is ubiquitous in HPC and we use a lot of computing power in LHC physics, so the arguments for the use of Linux in HPC are very similar to the arguments for the use of Linux in LHC physics analyses. Naturally, it's important to have an operating system that is free, open source and reliable (Scientific Linux is basically Red Hat Linux), but here's a quotation from the Scientific Linux website that should give some idea of why Scientific Linux is needed:And he also writes about Apple and Comic Sans:
"Our main goal for the base distribution is to have everything compatible with Enterprise, with only a few minor additions or changes. Examples of items that were added are Alpine, and OpenAFS.
Our secondary goal is to allow easy customization for a site, without disturbing the Scientific Linux base. The various labs are able to add their own modifications to their own site areas. By the magic of scripts, and the anaconda installer, each site is to be able to create their own distributions with minimal effort. Or, if a user wishes, they can simply install the base SL release."
I work primarily in physics, not in computing, so I doubt that I am able to argue very competently for Linux over something such as BSD. The fact is that Linux was the operating system used in the overwhelming majority of the analyses contributing to the discovery, so, in that sense I think I am justified in claiming that Linux played a vital role in the discovery.
In many ways, some Apple fans are similar to religious people in their devotion to something; that is, their support is not really derived from a critical appraisal of the technical standard of Apple products. I don't identify with this kind of motivation, but I am much happier seeing people religiously attached to new technological gadgetry than to invisible sky daddies.And finally he explain (one of many) that, with the data collected since june 2012, we can say that the new particle is a new boson, but we are not certain that it is a Higgs boson:
Similarly, Comic Sans is grotesque, but if it contributes to directing attention to the recent discovery, then it could be argued that it is a good thing.
In direct answer to your question, I think that you can thank Microsoft Bob for the existence of Comic Sans.
The properties of the discovered boson have yet to be scrutinised thoroughly before one can reliably claim it to be a Higgs boson (note that I do not claim the discovered boson to be the Higgs particle in the post). This is a phase of analysis we are now moving into.And don't forget to read the post about the discover of the new boson!
