Showing papers in "Journal of Physics G in 2007"
TL;DR: In this article, the authors present a detailed analysis of the performance of the Large Hadron Collider (CMS) at 14 TeV and compare it with the state-of-the-art analytical tools.
Abstract: 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, Bs 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 Z0 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 ET, 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
973 citations
TL;DR: In this article, the experimental investigation of the decay properties of the heavy nuclei is presented, and the obtained results are discussed in the context of the theoretical predictions about the island of stability of the hypothetical superheavy elements.
Abstract: After a brief introduction of the role of shell effects in determining the limiting nuclear masses, the experimental investigation of the decay properties of the heaviest nuclei is presented. For the production of superheavy nuclides fusion, reactions of heavy actinide nuclei with 48Ca-projectiles have been used. The properties of the new nuclei, the isotopes of elements 112–118, as well as of their decay products, together with the known data for the light isotopes with Z ≤ 113, give evidence of the significant increase of the stability with the neutron number of the heavy nucleus. The obtained results are discussed in the context of the theoretical predictions about the 'island of stability' of the hypothetical superheavy elements.
606 citations
TL;DR: In this paper, the capabilities of the CERN Large Hadron Collider (LHC) experiment to explore the rich heavy-ion physics program offered by the LHC are presented, and the potential of the CMS experiment to carry out a series of representative Pb-Pb measurements.
Abstract: This report presents the capabilities of the CMS experiment to explore the rich heavy-ion physics programme offered by the CERN Large Hadron Collider (LHC). The collisions of lead nuclei at energies , will probe quark and gluon matter at unprecedented values of energy density. The prime goal of this research is to study the fundamental theory of the strong interaction ? Quantum Chromodynamics (QCD) ? in extreme conditions of temperature, density and parton momentum fraction (low-x).This report covers in detail the potential of CMS to carry out a series of representative Pb-Pb measurements. These include bulk observables, (charged hadron multiplicity, low pT inclusive hadron identified spectra and elliptic flow) which provide information on the collective properties of the system, as well as perturbative probes such as quarkonia, heavy-quarks, jets and high pT hadrons which yield tomographic information of the hottest and densest phases of the reaction.
361 citations
TL;DR: In this article, the muon magnetic moment and its role in supersymmetry phenomenology is discussed, and numerical examples are given and the dominant tan β sign(μ)/M2SUSY behaviour is qualitatively explained.
Abstract: The present review is devoted to the muon magnetic moment and its role in supersymmetry phenomenology. Analytical results for the leading supersymmetric one- and two-loop contributions are provided, numerical examples are given and the dominant tan β sign(μ)/M2SUSY behaviour is qualitatively explained. The consequences of the Brookhaven measurement are discussed. The 2σ deviation from the standard model prediction implies preferred ranges for supersymmetry parameters, in particular upper and lower mass bounds. Correlations with other observables from collider physics and cosmology are reviewed. We attempt to give, wherever possible, an intuitive understanding of each result before providing a detailed discussion.
238 citations
TL;DR: In this paper, a robust adaptive method is presented that is able to cope with contaminated data, formulated as an iterative re-weighted Kalman filter and Annealing is introduced to avoid local minima in the optimization.
Abstract: Vertex fitting frequently has to deal with both mis-associated tracks and mis-measured track errors. A robust, adaptive method is presented that is able to cope with contaminated data. The method is formulated as an iterative re-weighted Kalman filter. Annealing is introduced to avoid local minima in the optimization. For the initialization of the adaptive filter a robust algorithm is presented that turns out to perform well in a wide range of applications. The tuning of the annealing schedule and of the cut-off parameter is described using simulated data from the CMS experiment. Finally, the adaptive property of the method is illustrated in two examples.
214 citations
TL;DR: A detailed survey of the experimental studies and theoretical interpretation of nucleon electromagnetic form factors can be found in this article, where the authors provide a succinct survey of some of the most relevant works.
Abstract: Elastic electromagnetic nucleon form factors have long provided vital information about the structure and composition of these most basic elements of nuclear physics. The form factors are a measurable and physical manifestation of the nature of the nucleons' constituents and the dynamics that binds them together. Accurate form factor data obtained in recent years using modern experimental facilities has spurred a significant reevaluation of the nucleon and pictures of its structure; e.g., the role of quark orbital angular momentum, the scale at which perturbative QCD effects should become evident, the strangeness content, and meson-cloud effects. We provide a succinct survey of the experimental studies and theoretical interpretation of nucleon electromagnetic form factors.
161 citations
TL;DR: In this paper, the structure of heavy baryons containing a charm or a bottom quark was investigated by means of the Faddeev method in momentum space, which is consistent with the light-baryon spectra.
Abstract: We investigate the structure of heavy baryons containing a charm or a bottom quark. We employ a constituent quark model successful in the description of the baryon–baryon interaction which is consistent with the light-baryon spectra. We solve exactly the three-quark problem by means of the Faddeev method in momentum space. Heavy-baryon spectrum shows a manifest compromise between perturbative and nonperturbative contributions. The flavour dependence of the one-gluon exchange is analysed. We assign quantum numbers to some already observed resonances, and we predict the first radial and orbital excitations of all states with J = 1/2 or 3/2. We combine our results with heavy-quark symmetry and lowest order SU(3) symmetry breaking to predict the masses and quantum numbers of six still non-measured ground-state beauty baryons.
155 citations
TL;DR: In this article, the critical point symmetries (CPS) X (5) and E(5) are compared to the data in a number of nuclei and mass regions.
Abstract: Recently, the idea of quantum phase transitions has been applied to equilibrium shape changes in finite atomic nuclei. An introduction to and discussion of this concept, both from the macroscopic perspective and from a microscopic approach, in terms of shell structure and residual interactions is presented. Following this, the quantitative predictions of the critical point symmetries (CPS) X(5) and E(5) are discussed in some detail and compared to the data in a number of nuclei and mass regions. Any successful new model paradigm soon generates modifications to improve the predictions and, likewise, often spawns related models inspired by the original ansatz. This is eminently true of the CPS and we make an effort to briefly discuss this rapidly advancing area in terms of a number of recent modifications to the CPS as well as related models that are couched in a geometrical perspective.
128 citations
TL;DR: In this paper, the LIT method has been used for ab initio calculations of electroweak cross sections in light nuclear systems, and their implications for the present understanding of microscopic nuclear dynamics are discussed.
Abstract: The LIT method has allowed ab initio calculations of electroweak cross sections in light nuclear systems. This review presents a description of the method from both a general and a more technical point of view, as well as a summary of the results obtained by its application. The remarkable features of the LIT approach, which make it particularly efficient in dealing with a general reaction involving continuum states, are underlined. Emphasis is given on the results obtained for electroweak cross sections of few-nucleon systems. Their implications for the present understanding of microscopic nuclear dynamics are discussed.
120 citations
TL;DR: In this article, the pseudorapidity and azimuthal correlations between high-P t charged hadrons in √SΝΝ = 200 GeV Au+Au collisions are presented.
Abstract: Systematic measurements of pseudorapidity (Δn) and azimuthal (A0) correlations between high-P t charged hadrons in √SΝΝ = 200 GeV Au+Au collisions are presented. An enhancement of correlated yield at large Δη on the near side is observed. This effect persists up to trigger p t trig ∼ 9 GeV/c, indicating that it is associated with jet production. A more detailed analysis suggests distinct short-range and long-range components in the correlation.
115 citations
TL;DR: In this article, the authors reported the first measurements of W and Z boson cross-sections times the corresponding leptonic branching ratios for collisions at TeV based on the decays of the W and z bosons into electrons and muons.
Abstract: We report the first measurements of inclusive W and Z boson cross-sections times the corresponding leptonic branching ratios for collisions at TeV based on the decays of the W and Z bosons into electrons and muons. The data were recorded with the CDF II detector at the Fermilab Tevatron and correspond to an integrated luminosity of 72.0 ± 4.3 pb−1. We test e-μ lepton universality in W decays by measuring the ratio of the W → μν to W → eν cross sections and determine a value of 0.991 ± 0.004(stat.) ± 0.011(syst.) for the ratio of W − l − ν couplings (gμ/ge). Since there is no sign of non-universality, we combine our cross-section measurements in the different lepton decay modes and obtain nb and pb for dilepton pairs in the mass range between 66 GeV/c2 and 116 GeV/c2. We compute the ratio R of the W → lν to Z → ll cross sections taking all correlations among channels into account and obtain R = 10.84 ± 0.15(stat.) ± 0.14(syst.) including a correction for the virtual photon exchange component in our measured γ*/Z → ll cross section. Based on the measured value of R, we extract values for the W leptonic branching ratio, Br(W → lν)= 0.1082 ± 0.0022; the total width of the W boson, Γ(W)= 2092 ± 42 MeV; and the ratio of W and Z boson total widths, Γ(W)/Γ(Z)= 0.838 ± 0.017. In addition, we use our extracted value of Γ(W) whose value depends on various electroweak parameters and certain CKM matrix elements to constrain the Vcs CKM matrix element, |Vcs| = 0.976 ± 0.030.
TL;DR: In this paper, an overview of the main methods used to determine the nucleus-nucleus optical potential (OP) is presented, which is the key to explore this interesting process.
Abstract: Elastic scattering of α-particles and some tightly bound light nuclei has shown the pattern of rainbow scattering at medium energies, which is due to the refraction of the incident wave by a strongly attractive nucleus–nucleus potential. This review gives an introduction to the physics of the nuclear rainbow based essentially on the optical model description of the elastic scattering. Since the realistic nucleus–nucleus optical potential (OP) is the key to explore this interesting process, an overview of the main methods used to determine the nucleus–nucleus OP is presented. Given the fact that the absorption in a rainbow system is much weaker than that usually observed in elastic heavy-ion scattering, the observed rainbow patterns were shown to be linked directly to the density overlap of the two nuclei penetrating each other in the elastic channel, with a total density reaching up to twice the nuclear matter saturation density ρ0. For the calculation of the nucleus–nucleus OP in the double-folding model, a realistic density dependence has been introduced into the effective M3Y interaction which is based originally on the G-matrix elements of the Reid and Paris nucleon–nucleon (NN) potentials. Most of the elastic rainbow scattering data were found to be best described by a deep real OP like the folded potential given by this density-dependent M3Y interaction. Within the Hartree–Fock formalism, the same NN interaction gives consistently a soft equation of state of cold nuclear matter which has an incompressibility constant K≈ 230–260 MeV. Our folding analysis of numerous rainbow systems has shown that the elastic α-nucleus and nucleus–nucleus refractive rainbow scattering is indeed a very helpful experiment for the determination of the realistic K value. The refractive rainbow-like structures observed in other quasi-elastic scattering reactions have also been discussed. Some evidences for the refractive effect in the elastic scattering of unstable nuclei are presented and perspectives for future studies are discussed.
TL;DR: In this paper, an algebraic approach to the neutrino propagation in dense media is presented, where the Hamiltonian describing a gas of neutrinos interacting with each other and with background fermions is written in terms of the appropriate SU(N) operators.
Abstract: An algebraic approach to the neutrino propagation in dense media is presented. The Hamiltonian describing a gas of neutrinos interacting with each other and with background fermions is written in terms of the appropriate SU(N) operators, where N is the number of neutrino flavours. The evolution of the resulting many-body problem is formulated as a coherent-state path integral. Some commonly used approximations are shown to represent the saddle-point solution of the path integral for the full many-body system.
TL;DR: In this article, the dynamics of heavy-ion low-energy collisions are studied within the realistic model based on multi-dimensional Langevin equations, and the interplay of strongly coupled deep inelastic scattering, quasi-fission and fusion fission processes is discussed.
Abstract: The dynamics of heavy-ion low-energy collisions is studied within the realistic model based on multi-dimensional Langevin equations. Interplay of strongly coupled deep inelastic scattering, quasi-fission and fusion-fission processes is discussed. Collisions of very heavy nuclei ( 238 U+ 238 U, 232 Th+ 250 Cf and 238 U+ 448 Cm) are investigated as an alternative way for the production of super-heavy elements with increasing neutron number. Large charge and mass transfer were found in these reactions due to the inverse (anti-symmetrizing) quasi-fission process leading to the formation of surviving super-heavy long-lived neutron-rich nuclei. In many events the lifetime of the composite giant system consisting of two touching nuclei turns out to be rather long (≥10 -20 s), sufficient for observing line structure in spontaneous positron emission from super-strong electric fields, a fundamental QED process.
TL;DR: A brief overview of the problem of quark confinement in hadronic physics and a few of the suggested explanations of the confining force can be found in this paper, along with a discussion of some of the proposed explanations.
Abstract: We give a brief overview of the problem of quark confinement in hadronic physics and outline a few of the suggested explanations of the confining force.
TL;DR: A review of nucleosynthesis studies can be found in this article, with special emphasis on recent advances in nova theory (including multidimensional models) as well as on experimental efforts to reduce nuclear uncertainties affecting critical reaction rates.
Abstract: Classical novae are fascinating stellar explosions at the crossroads of stellar astrophysics, nuclear physics, and cosmochemistry. In this review, we briefly summarize 30 years of nucleosynthesis studies, with special emphasis on recent advances in nova theory (including multidimensional models) as well as on experimental efforts to reduce nuclear uncertainties affecting critical reaction rates. Among the topics that are covered, we outline the interplay between nova outbursts and the galactic chemical abundances, the synthesis of radioactive nuclei of interest for γ-ray astronomy, such as 7Li, 22Na or 26Al, and the potential discovery of presolar meteoritic grains likely condensed in nova shells.
TL;DR: In this article, the authors conduct a review of experimental results on ultra-high energy cosmic rays (UHECRs) including measurements of the features of the spectrum, the composition of the primary particle flux and the search for anisotropy in event arrival direction.
Abstract: We conduct a review of experimental results on ultra-high energy cosmic rays (UHECRs) including measurements of the features of the spectrum, the composition of the primary particle flux and the search for anisotropy in event arrival direction. We find that while there is a general consensus on the features in the spectrum—the Second Knee, the Ankle and (to a lesser extent) the GZK Cutoff—there is little consensus on the composition of the primaries that accompany these features. This lack of consensus on the composition makes interpretation of the agreed upon features problematic. There is also little direct evidence about potential sources of UHECRs, as early reports of arrival-direction anisotropies have not been confirmed in independent measurements.
TL;DR: In this paper, the dynamics of heavy-ion low-energy damped collisions are studied within the model based on the Langevin-type equations, and an enhanced yield of nuclides far from the projectile and target masses is found in multi-nucleon transfer reactions due to the shell effects.
Abstract: The dynamics of heavy-ion low-energy damped collisions is studied within the model based on the Langevin-type equations. Shell effects on the multidimensional potential energy surface play an important role in these reactions. An enhanced yield of nuclides far from the projectile and target masses was found in multi-nucleon transfer reactions due to the shell effects. Our theoretical predictions need experimental confirmation.
TL;DR: In this article, the properties of the wave equation for potentials depending on the energy with emphasis on confining potentials are studied. And the authors apply such a model to the description of heavy quark systems.
Abstract: We study the properties of the wave equation for potentials depending on the energy with emphasis on confining potentials. In this case, for a linear energy dependence, the spectrum shows a saturation effect: the eigenvalues reach a finite limit as the quantum numbers increase. The harmonic oscillator and the linear potentials are studied as examples admitting analytical solutions. We apply such a model to the description of heavy quark systems. We first present a toy model based on the harmonic oscillator and show its ability to reproduce the experimental spectra of charmonium and bottomium. In more realistic calculations, use is made of the Cornell potential for the radial shape and an energy dependence more general than the linear assumption. Comparing the results with those of conventional potentials, we discuss to what extent energy-dependent potentials can bring new features in the description of heavy quark systems. Finally, we show that the energy dependence of the potential has a clear influence on the saturation of the spectrum.
TL;DR: In this paper, the authors present the many-body theory of nuclear matter as developed along different years and with different methods, and compare the different methods at a formal level, as well as the final nuclear equation of state calculated within each one of the considered many body schemes.
Abstract: A central issue in the theory of astrophysical compact objects and heavy-ion reactions at intermediate and relativistic energies is the nuclear equation of state (EoS). On the one hand, the large and expanding set of experimental and observational data is expected to constrain the behaviour of the nuclear EoS, especially at density above saturation, where it is directly linked to fundamental processes which can occur in dense matter. On the other hand, theoretical predictions for the EoS at high density can be challenged by the phenomenological findings. In this topical review paper, we present the many-body theory of nuclear matter as developed along different years and with different methods. Only nucleonic degrees of freedom are considered. We compare the different methods at a formal level, as well as the final EoS calculated within each one of the considered many-body schemes. The outcome of this analysis should help in restricting the uncertainty of the theoretical predictions for the nuclear EoS.
TL;DR: The status of the field of ultrahigh energy cosmic-ray physics is summarized, from the point of view of the latest results of the High-Resolution Fly's Eye (HiRes) Experiment as discussed by the authors.
Abstract: The status of the field of ultrahigh energy cosmic-ray physics is summarized, from the point of view of the latest results of the High-Resolution Fly's Eye (HiRes) Experiment. HiRes results are presented, and compared with those of the Akeno Giant Air Shower Array (AGASA), plus the Telescope Array and Pierre Auger experiments. The HiRes measurement of the cosmic-ray spectrum and the observation of the GZK cutoff are presented. HiRes results on composition, searches for anisotropy, measurement of the proton-air total cross-section and shapes of shower profiles are presented.
TL;DR: In this article, a technique for estimating the number of future 0νββ results using several distinct nuclei to optimize the physics reach of upcoming experiments is presented, which can be used as guidance for the upcoming theoretical and experimental programs.
Abstract: We present a technique for estimating the number of future 0νββ results using several distinct nuclei to optimize the physics reach of upcoming experiments. We use presently available matrix-element calculations and simulated sets of predicted 0νββ measured rates in multiple isotopes to estimate the required precision and number of experiments to discern the underlying physics governing the mechanism of the process. Our results indicate that three (four) experimental results with total uncertainty (statistical, systematic, theoretical) of less than ~20% (~40%) can elucidate the underlying physics. If the theoretical (i.e. matrix-element) uncertainty contribution is below ~18%, then three or four experimental results of ~20% precision (statistical and systematic) are required. These uncertainty goals can be taken as guidance for the upcoming theoretical and experimental programs.
TL;DR: In this article, a review of light-quark mesons, glueballs, hybrids, particles with a single c or b quark, charmonium (cc) and bottomonium (bb) states is presented.
Abstract: Many new results on hadron spectra have been appearing in the past few years thanks to improved experimental techniques and searches in new channels New theoretical techniques including refined methods of lattice QCD have kept pace with these developments Much has been learned about states made of both light (u, d and s) and heavy (c, b) quarks The present review treats light-quark mesons, glueballs, hybrids, particles with a single c or b quark, charmonium (cc) and bottomonium (bb) states Some prospects for further study are noted
TL;DR: In this paper, the effects of the intrinsic charm on the hadronic production of Xi(cc) are studied and the numerical results for SELEX show that by considering all the contributions from various sub-processes, the predicted cross section may be enhanced by a factor so big as 10(2) due to a modulating intrinsic charm.
Abstract: The effects of the intrinsic charm on the hadronic production of Xi(cc) are studied. By taking reasonable intrinsic charm component into account, the change of the theoretical prediction on the production of Xi(cc) for LHC and Tevatron is small, but in contrast it may enhance significantly for SELEX. The reason is that the collision energy at LHC and Tevatron is so large that the gluon-gluon fusion sub-process, which is irrelevant to intrinsic charm, becomes dominant. But the situation for SELEX is quite different. Our numerical results for SELEX show that by considering all the contributions from various sub-processes, the predicted cross section may be enhanced by a factor so big as 10(2) due to a modulating intrinsic charm being taken into account. Therefore, the hadronic production of Xi(cc) at SELEX may be sensitive enough in observing the intrinsic charm inside the incident hadrons.
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TL;DR: A concise review of the experimental and phenomenological progress in high-energy heavy-ion physics over the past few years is presented in this article, focusing on measurements at BNL-RHIC and CERN-SPS which provide information on fundamental properties of QCD matter at extreme values of temperature, density and low-x.
Abstract: A concise review of the experimental and phenomenological progress in high-energy heavy-ion physics over the past few years is presented. Emphasis is put on measurements at BNL-RHIC and CERN-SPS which provide information on fundamental properties of QCD matter at extreme values of temperature, density and low-x. The new opportunities accessible at the LHC, which may help clarify some of the current open issues, are also outlined.
TL;DR: In this article, the covariant light-front approach is applied to ground-state heavy quarkonium and the pesudoscalar and vector meson decay constants are discussed.
Abstract: The light-front approach is a relativistic quark model and offers many insights into the internal structures of the hadronic bound states. In this study, we apply the covariant light-front approach to ground-state heavy quarkonium. The pesudoscalar and vector meson decay constants are discussed. We present a detailed study of two-photon annihilation P → γγ and magnetic dipole transition V → Pγ processes. The numerical predictions of the light-front approach are consistent with the experimental data and those in other approaches. The relations of the light-front approach with the other methods are discussed in brief.
TL;DR: In this article, the authors used chiral effective theory to predict the deuteron form factor ratio G C /G Q as well as ratios of deuterons to nucleon form factors.
Abstract: We use chiral effective theory ( Χ ET) to predict the deuteron form factor ratio G C /G Q as well as ratios of deuteron to nucleon form factors. These ratios are calculated to next-to-next-to-leading order. At this order the chiral expansion for the NN isoscalar charge operator (including consistently calculated 1/M corrections) is a parameter-free prediction of the effective theory. Use of this operator in conjunction with NLO and NNLO Χ ET wavefunctions produces results that are consistent with extant experimental data for Q 2 < 0.35 GeV 2 . These wavefunctions predict a deuteron quadrupole moment G Q (Q 2 = 0) = 0.278-0.282 fm 2 -with the variation arising from short-distance contributions to this quantity. The variation is of the same size as the discrepancy between the theoretical result and the experimental value. This motivates the renormalization of G Q via a two-nucleon operator that couples to quadrupole photons. After that renormalization we obtain a robust prediction for the shape of G C /G Q at Q 2 < 0.3 GeV 2 . This allows us to make precise, model-independent predictions for the values of this ratio that will be measured at the lower end of the kinematic range explored at BLAST. We also present results for the ratio G C /G M .
TL;DR: In this paper, the spectrum of the corresponding fractional symmetric rigid rotor is discussed, and it is shown that the rotational, vibrational and γ-unstable limits of the standard geometric collective models are particular limits of this spectrum.
Abstract: Based on the Riemann fractional derivative the Casimir operators and multiplets for the fractional extension of the rotation group SO(n) are calculated algebraically. The spectrum of the corresponding fractional symmetric rigid rotor is discussed. It is shown that the rotational, vibrational and γ-unstable limits of the standard geometric collective models are particular limits of this spectrum. A comparison with the ground-state band spectra of nuclei shows an agreement with experimental data better than 2%. The derived results indicate that the fractional symmetric rigid rotor is an appropriate tool for a description of low-energy nuclear excitations.
TL;DR: In this article, a modified relation between the black hole mass and temperature is employed to simulate micro-black hole evaporation at the LHC, where the usual assumption that black holes explode around 1 TeV is also released.
Abstract: We study possible back-reaction and quantum gravity effects in the evaporation of black holes which could be produced at the LHC through a modification of the Hawking emission. The corrections are phenomenologically taken into account by employing a modified relation between the black hole mass and temperature. The usual assumption that black holes explode around 1 TeV is also released, and the evaporation process is extended to (possibly much) smaller final masses. We show that these effects could be observable for black holes produced with a relatively large mass and should therefore be taken into account when simulating micro-black hole events for the experiments planned at the LHC.
TL;DR: In this paper, BES data on the σ pole are refitted taking into account new information on coupling of σ to KK and ηη channels, and they give a pole position of 500 ± 30 − i(264 ± 30) MeV.
Abstract: BES data on the σ pole are refitted taking into account new information on coupling of σ to KK and ηη. The fit also includes CERN–Munich data on ππ elastic phases shifts and Ke4 data, and gives a pole position of 500 ± 30 − i(264 ± 30) MeV. There is a clear discrepancy with the σ pole position recently predicted by Caprini et al (2006 Phys. Rev. Lett. 96 032001) using the Roy equation. This discrepancy may be explained naturally by uncertainties arising from inelasticity in KK and ηη channels and mixing between σ and f0(980). Adding freedom to accommodate these uncertainties gives an optimum compromise with a pole position of 472 ± 30 − i(271 ± 30) MeV.