In the last 30 days

• Open/close Review of Particle Physics

  K Nakamura (Particle Data Group) 2010 J. Phys. G: Nucl. Part. Phys. 37 075021 Tag this article

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  This biennial Review summarizes much of particle physics. Using data from previous editions, plus 2158 new measurements from 551 papers, we list, evaluate, and average measured properties of gauge bosons, leptons, quarks, mesons, and baryons. We also summarize searches for hypothetical particles such as Higgs bosons, heavy neutrinos, and supersymmetric particles. All the particle properties and search limits are listed in Summary Tables. We also give numerous tables, figures, formulae, and reviews of topics such as the Standard Model, particle detectors, probability, and statistics. Among the 108 reviews are many that are new or heavily revised including those on neutrino mass, mixing, and oscillations, QCD, top quark, CKM quark-mixing matrix, V _ud & V _us, V _cb & V _ub, fragmentation functions, particle detectors for accelerator and non-accelerator physics, magnetic monopoles, cosmological parameters, and big bang cosmology.

  A booklet is available containing the Summary Tables and abbreviated versions of some of the other sections of this full Review. All tables, listings, and reviews (and errata) are also available on the Particle Data Group website: pdg.lbl.gov.

• Open/close Review of Particle Physics

  W-M Yao et al 2006 J. Phys. G: Nucl. Part. Phys. 33 1 Tag this article

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  This biennial Review summarizes much of particle physics. Using data from previous editions, plus 2633 new measurements from 689 papers, we list, evaluate, and average measured properties of gauge bosons, leptons, quarks, mesons, and baryons. We also summarize searches for hypothetical particles such as Higgs bosons, heavy neutrinos, and supersymmetric particles. All the particle properties and search limits are listed in Summary Tables. We also give numerous tables, figures, formulae, and reviews of topics such as the Standard Model, particle detectors, probability, and statistics. Among the 110 reviews are many that are new or heavily revised including those on CKM quark-mixing matrix, V _ud & V _us, V _cb & V _ub, top quark, muon anomalous magnetic moment, extra dimensions, particle detectors, cosmic background radiation, dark matter, cosmological parameters, and big bang cosmology.
       A booklet is available containing the Summary Tables and abbreviated versions of some of the other sections of this full Review. All tables, listings, and reviews (and errata) are also available on the Particle Data Group website: http://pdg.lbl.gov.

• Open/close Presentation of search results: the CL_s technique

  A L Read 2002 J. Phys. G: Nucl. Part. Phys. 28 2693 Tag this article

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  I describe a framework for the presentation of search results which is motivated by frequentist statistics. The most well-known use of this framework is for the combined search for the Higgs boson at LEP. A toy neutrino oscillations experiment is used to illustrate the rich information available in the framework for exclusion and discovery. I argue that the so-called CL _s technique for setting limits is appropriate for determining exclusion intervals while the determination of confidence intervals advocated by Feldman and Cousins' method is more appropriate for treating established signals, i.e. going beyond discovery to measurement.

  (From the workshop 'Advanced Statistical Techniques in Particle Physics', 18–22 March 2002)

• Open/close TeV gamma-ray observations of Markarian 421 using TACTIC during 2009–10

  P Chandra et al 2012 J. Phys. G: Nucl. Part. Phys. 39 045201 Tag this article

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  We have observed the blazar Markarian 421 with the TACTIC γ-ray telescope at Mt. Abu, India, from 22 November 2009 to 16 May 2010 for 265 h. Detailed analysis of the data so recorded revealed the presence of a TeV γ-ray signal with a statistical significance of 12.12σ at E _γ ⩾ 1 TeV. We have estimated the time-averaged differential energy spectrum of the source in the energy range 1.0–16.44 TeV. The spectrum fits well with the power-law function of the form (d F/d E = f ₀ E ^−Γ) with f ₀ = (1.39 ± 0.239) × 10 ⁻¹¹ cm ⁻² s ⁻¹ TeV ⁻¹ and Γ = 2.31 ± 0.14.

• Open/close Azimuthal angular dependence study of the atmospheric muon charge ratio at sea level using Geant4

  Halil Arslan and Mehmet Bektasoglu 2012 J. Phys. G: Nucl. Part. Phys. 39 055201 Tag this article

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  The azimuth dependence of the cosmic muon charge ratio at sea level was estimated using the Geant4 simulation package. Simulations were separately run at 12 azimuth angles ranging from 0° to 330° with 30° increment. Two hundred thousand proton and alpha particles were randomly distributed over the zenith angle range 30° < θ < 40° at each azimuth angle. The kinetic energy spectra of proton and helium nuclei were taken from the balloon-flight measurements. The atmospheric muon charge ratio was calculated at each azimuthal angle for low energy muons with a mean momentum around 0.5 GeV/ c. The Geant4 simulation results have been compared with those of the CORSIKA simulation program and with the WILLI measurements. The simulation results reproduce well the measured east–west effect with a non-zero asymmetry A _EW = 0.24. This asymmetry in the charge ratio decreases from 0.37 to 0.19 as the momentum increases from 0.22 to 0.70 GeV/ c.

• Open/close CMS Physics Technical Design Report, Volume II: Physics Performance

  The CMS Collaboration 2007 J. Phys. G: Nucl. Part. Phys. 34 995 Tag this article

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  CMS is a general purpose experiment, designed to study the physics of pp collisions at 14 TeV at the Large Hadron Collider (LHC). It currently involves more than 2000 physicists from more than 150 institutes and 37 countries. The LHC will provide extraordinary opportunities for particle physics based on its unprecedented collision energy and luminosity when it begins operation in 2007.

  The principal aim of this report is to present the strategy of CMS to explore the rich physics programme offered by the LHC. This volume demonstrates the physics capability of the CMS experiment. The prime goals of CMS are to explore physics at the TeV scale and to study the mechanism of electroweak symmetry breaking—through the discovery of the Higgs particle or otherwise. To carry out this task, CMS must be prepared to search for new particles, such as the Higgs boson or supersymmetric partners of the Standard Model particles, from the start-up of the LHC since new physics at the TeV scale may manifest itself with modest data samples of the order of a few fb ⁻¹ or less.

  The analysis tools that have been developed are applied to study in great detail and with all the methodology of performing an analysis on CMS data specific benchmark processes upon which to gauge the performance of CMS. These processes cover several Higgs boson decay channels, the production and decay of new particles such as Z' and supersymmetric particles, B _s production and processes in heavy ion collisions. The simulation of these benchmark processes includes subtle effects such as possible detector miscalibration and misalignment. Besides these benchmark processes, the physics reach of CMS is studied for a large number of signatures arising in the Standard Model and also in theories beyond the Standard Model for integrated luminosities ranging from 1 fb ⁻¹ to 30 fb ⁻¹. The Standard Model processes include QCD, B-physics, diffraction, detailed studies of the top quark properties, and electroweak physics topics such as the W and Z ⁰ boson properties. The production and decay of the Higgs particle is studied for many observable decays, and the precision with which the Higgs boson properties can be derived is determined. About ten different supersymmetry benchmark points are analysed using full simulation. The CMS discovery reach is evaluated in the SUSY parameter space covering a large variety of decay signatures. Furthermore, the discovery reach for a plethora of alternative models for new physics is explored, notably extra dimensions, new vector boson high mass states, little Higgs models, technicolour and others. Methods to discriminate between models have been investigated.

  This report is organized as follows. Chapter 1, the Introduction, describes the context of this document. Chapters 2–6 describe examples of full analyses, with photons, electrons, muons, jets, missing E _T, B-mesons and τ's, and for quarkonia in heavy ion collisions. Chapters 7–15 describe the physics reach for Standard Model processes, Higgs discovery and searches for new physics beyond the Standard Model.

• Open/close Microscopic optical potentials for nucleon–nucleus scattering at 65 MeV

  Dipti Pachouri et al 2012 J. Phys. G: Nucl. Part. Phys. 39 055101 Tag this article

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  Microscopic optical potentials for nucleon–nucleus scattering obtained from folding the calculated G-matrices with RMF densities of the target have been used to analyze the 65 MeV proton and neutron–nucleus scattering data over a wide mass region. The soft-core Argonne AV14, AV18 and the old hard-core Hamada–Johnston inter-nucleon potentials have been used to calculate the G-matrices in the Brueckner–Hartree–Fock approach. The calculated potentials have been used to analyze the differential elastic cross-section, analyzing power and spin-rotation function for neutron and proton scattering at 65 MeV from ¹²C to ²⁰⁸Pb. Our results are in satisfactory agreement with the experimental data. Comparison of our results with phenomenological optical model analyses is also presented. Mass number dependence of the mean square radii of real central optical potential ⟨ r ²⟩ _pot. for the microscopic potentials used here is found to be in close agreement with each other as well as with empirical results. We also present our results for proton reaction cross-section from ¹²C to ⁹⁰Zr in the energy region 20–200 MeV.

• Open/close The odd–even effect of ²⁰Ne fragmentation cross sections

  J X Cheng et al 2012 J. Phys. G: Nucl. Part. Phys. 39 055104 Tag this article

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  Projectile fragmentation cross sections are calculated for reactions of ²⁰Ne on the C, Al, Cu, Sn and Pb targets at 400 A MeV by using the improved quantum molecular dynamics model together with the statistical model code GEMINI. The improved quantum molecular dynamics model is applied to describe the dynamical process, and the GEMINI model is used to simulate the de-excitation process of excited primary fragments. It is found that the total cross sections increase as a function of the target mass, which is in good agreement with the experimental results and other theoretical predictions. The odd–even effect of the partial cross sections observed in experiments is well reproduced, which appears in the de-excitation process of the excited primary fragments as a result of pairing effect and is mainly formed in the grazing collisions. The results of isospin distributions demonstrate that the odd–even effect of partial cross sections mainly comes from the fragments with T _Z = 0, ±0.5.

• Open/close Low-energy nuclear spectroscopy in a microscopic multiphonon approach

  N Lo Iudice et al 2012 J. Phys. G: Nucl. Part. Phys. 39 043101 Tag this article

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  The low-lying spectra of heavy nuclei are investigated within the quasiparticle–phonon model. This microscopic approach goes beyond the quasiparticle random-phase approximation by treating a Hamiltonian of separable form in a microscopic multiphonon basis. It is therefore able to describe the anharmonic features of collective modes as well as the multiphonon states, whose experimental evidence is continuously growing. The method can be put in close correspondence with the proton–neutron interacting boson model. By associating the microscopic isoscalar and isovector quadrupole phonons with proton–neutron symmetric and mixed-symmetry quadrupole bosons, respectively, the microscopic states can be classified, just as in the algebraic model, according to their phonon content and their symmetry. In addition, these states disclose the nuclear properties which are to be ascribed to genuine shell effects, not included in the algebraic approach. Due to its flexibility, the method can be implemented numerically for systematic studies of spectroscopic properties throughout entire regions of vibrational nuclei. The spectra and multipole transition strengths so computed are in overall good agreement with the experimental data. By exploiting the correspondence of the method with the interacting boson model, it is possible to embed the microscopic states into this algebraic frame and, therefore, face the study of nuclei far from shell closures, not directly accessible to merely microscopic approaches. Here, it is shown how this task is accomplished through systematic investigations of magnetic dipole and, especially, electric dipole modes along paths moving from the vibrational to the transitional regions. The method is very well suited to the study of well-deformed nuclei. It provides reliable descriptions of low-lying magnetic as well as electric multipole modes of nuclei throughout the rare-earth and actinide regions. Attention is focused here on the low-lying 0 ⁺ states produced in large abundance in recent experiments. The analysis shows that the quasiparticle–phonon model accounts for the occurrence of so many 0 ⁺ levels and discloses their nature.

• Open/close Focus section on AdS/CFT applications to QCD matter

  Steffen A Bass and Jorge Casalderrey-Solana 2012 J. Phys. G: Nucl. Part. Phys. 39 050301 Tag this article

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  The gauge/gravity duality is a remarkable correspondence between a large class of non-abelian field theories and gravitational theories in a curved background. In its original form, as discovered by Maldacena in the late 1990s [1], the AdS/CFT correspondence relates = 4 supersymmetric Yang–Mills (SYM) to type II B string theory in an AdS ₅ x S ⁵ background; but since then, many other realizations of the duality have been explored. One of the features that makes this approach unique is the fact that it generically relates the strong coupling limit of a gauge theory to weakly coupled classical gravity. In this way, the correspondence provides a unique access to the dynamics of gauge theories at strong coupling, a regime of those theories which is hard to treat otherwise. This feature is, in part, responsible for the on-going very intense research on the gauge/gravity duality, which has become one of the most exciting fields of theoretical physics nowadays.

  While in the recent past the correspondence has been applied to many different fields, one of the areas where this new tool has had a larger impact is the description of non-perturbative aspects of QCD matter. The influence of this method is due, in part, to the experimental findings of the heavy ion programs of RHIC and the LHC, which indicate that deconfined QCD matter, the quark–gluon plasma, in the region of the phase diagram accessible to experiments does not behave like a weakly coupled gas of quarks and gluons but rather like a fluid in which the plasma constituents suffer significant interactions. In particular, phenomenological analyses of the strong collective effects found in those collisions show that the ratio of the shear viscosity to entropy density for this matter is very small, η/s ~ 0.08. This small value is remarkably close to the celebrated value for the same quantity in = 4 SYM, η/s = 1/4 π obtained by Policastro et al in 2001 [2], making this computation one of the most influential results in the field and motivating a growing interest within the heavy ion and finite temperature QCD communities on the gauge/gravity duality.

  Since this influential work, the gauge/gravity duality has been applied to many different aspects of QCD at extreme conditions. A lot of effort has been made in using the correspondence in its original form to describe the high energy collision and thermalization of strongly coupled matter, as well as its interaction with energetic probes. While these results strictly apply to = 4 SYM, this large body of work has led to many insights into the equivalent problems in QCD, since in the region of relevance for current experiments the coupling is not small. Complementarily, there has been very intense research in the bottom-up construction of gravitational duals which capture some of the most salient differences between QCD and = 4 SYM, such as the lack of conformality, in the absence of supersymmetry. These new holographic models have been applied not only to collision dynamics, but also to the description of the QCD phase diagram.

  The intense research activity we have just described motivated a focus section on the applications of gauge/gravity duality to the dynamics of QCD matter under extreme conditions. The articles in this issue cover most of the aspects where the correspondence is currently having a larger impact within the field and will provide the reader with an overall view of the wide scope that this method has acquired, as well as the technical advances and main results in the field.

  References

  [1] Maldacena J 1999 The large- N limit of superconformal field theories and supergravity Int. J. Theor. Phys. 38 1113–33

  [2] Policastro G, Son D T and Starinets A O 2001 Shear viscosity of strongly coupled N = 4 supersymmetric Yang-Mills plasma Phys. Rev. Lett. 87 081601