- Prolate-Spherical Shape Coexistence at N=28 in ^{44} S
Author(s): C. Force, S. Grévy, L. Gaudefroy, O. Sorlin, L. Cáceres, F. Rotaru, J. Mrazek, N. L. Achouri, J. C. Angélique, F. Azaiez, B. Bastin, R. Borcea, A. Buta, J. M. Daugas, Z. Dlouhy, Zs. Dombrádi, F. De Oliveira, F. Negoita, Y. Penionzhkevich, M. G. Saint-Laurent, D. Sohler, M. Stanoiu, I. Stefan, C. Stodel, and F. Nowacki
The structure of ^{44} S has been studied by using delayed γ and electron spectroscopy. The decay rates of the 0_{2}^{+} isomeric state to the 2_{1}^{+} and 0_{1}^{+} states, measured for the first time, lead to a reduced transition probability B(E2: 2_{1}^{+} →0_{2}^{+} )=8.4(26) e^{2} fm^{4} and a monopole strength ρ^{2} (E0: 0_{2}^{+} →0_{1}^{+} )=8.7(7)×10^{-3} . Comparisons to shell model calculations point towards prolate-spherical shape coexistence, and a two-level mixing model is used to extract a weak mixing between the two configurations.
[Phys. Rev. Lett. 105, 102501] Published Wed Sep 01, 2010
- Hadron multiplicity in pp and AA collisions at LHC from the color glass condensate
Author(s): Eugene Levin and Amir H. Rezaeian
We provide quantitative predictions for the rapidity, centrality and energy dependencies of inclusive charged-hadron productions for the forthcoming LHC measurements in nucleus-nucleus collisions based on the idea of gluon saturation in the color-glass condensate framework. Our formulation gives very good descriptions of the first data from the LHC for the inclusive charged-hadron production in proton-proton collisions, the deep inelastic scattering at the Hadron-Elektron-Ring-Anlage at small Bjorken x, and the hadron multiplicities in nucleus-nucleus collisions at the Relativistic Heavy Ion Collider.
[Phys. Rev. D 82, 054003] Published Wed Sep 01, 2010
- Nonzero mean squared momentum of quarks in the nonperturbative QCD vacuum
Author(s): Li-Juan Zhou, Leonard S. Kisslinger, and Wei-xing Ma
The nonlocal vacuum condensates of QCD describe the distributions of quarks and gluons in the nonperturbative QCD vacuum. Physically, this means that vacuum quarks and gluons have nonzero mean squared momentum, called virtuality. In this paper we study the quark virtuality which is given by the ratio of the local quark-gluon mixed vacuum condensate to the quark local vacuum condensate. The two vacuum condensates are obtained by solving Dyson-Schwinger equations of a fully dressed quark propagator with an effective gluon propagator. Using our calculated condensates, we obtain the virtuality of quarks in the QCD vacuum state. Our numerical predictions are consistent with other theoretical model calculations such as QCD sum rules, lattice QCD and instanton models.
[Phys. Rev. D 82, 034037] Published Tue Aug 31, 2010
- Dielectric correction to the chiral magnetic effect
Author(s): Kenji Fukushima and Marco Ruggieri
We derive an electric current density j_{em} in the presence of a magnetic field B and a chiral chemical potential μ_{5} . We show that j_{em} has, not only the anomaly-induced term ∝μ_{5} B (i.e. chiral magnetic effect), but also a nonanomalous correction which comes from interaction effects and is expressed in terms of the susceptibility. We find the correction characteristically dependent on the number of quark flavors. The numerically estimated correction turns out to be a minor effect on heavy-ion collisions but can be tested by the lattice-QCD simulation.
[Phys. Rev. D 82, 054001] Published Wed Sep 01, 2010
- Intense few-cycle hard-UV-pulse-induced internal conversion processes
Author(s): Dániel Kis, Péter Kálmán, and Tamás Keszthelyi
The internal conversion coefficient for bound-free electron transition of originally energetically forbidden internal conversion processes induced by intense, few-cycle UV laser pulse of Gaussian shape in the case of isomers ^{107} Ag^{m} (K shell, E3, 25.47 keV), ^{90} Nb^{m} (L_{2} shell, M2+E3, 2.3 keV), ^{183} W^{m1} (M_{5} shell, E2, 1.79 keV), ^{183} W^{m2} (N_{1} shell, E1, 548 eV), and ^{188} Re^{m} (M_{2} shell, M3+E4, 2.63 keV), and ^{235} U^{m} (O_{4} and O_{5} shells, E3, 73.5 eV) is determined numerically. Experimental conditions and possibilities of the laser-induced internal conversion process of ^{183} W^{m2} from the N_{1} shell are discussed in more detail.
[Phys. Rev. A 82, 025401] Published Tue Aug 31, 2010
- Is the GSI anomaly due to neutrino oscillations? A real time perspective
Author(s): Jun Wu, Jimmy A. Hutasoit, Daniel Boyanovsky, and Richard Holman
We study a model for the “GSI anomaly” in which we obtain the time evolution of the population of parent and daughter particles directly in real time, considering explicitly the quantum entanglement between the daughter particle and neutrino mass eigenstates in the two-body decay. We confirm that the decay rate of the parent particle and the growth rate of the daughter particle do not feature a time modulation from interference of neutrino mass eigenstates. The lack of interference is a consequence of the orthogonality of the mass eigenstates. This result also follows from the density matrix obtained by tracing out the unobserved neutrino states. We confirm this result by providing a complementary explanation based on Cutkosky rules applied to the Feynman diagram that describes the self energy of the parent particle.
[Phys. Rev. D 82, 045027] Published Fri Aug 27, 2010
- Phase diagram of chiral quark matter: Color and electrically neutral Fulde-Ferrell phase
Author(s): Xu-Guang Huang and Armen Sedrakian
The phase diagram of charge and color neutral two-flavor color superconducting quark matter is studied including the homogeneous two-flavor superconductor (2SC) and the inhomogeneous Fulde-Ferrell (FF) phases within the Nambu-Jona-Lasinio model. The low-temperature domain T≤5 MeV of the phase diagram contains the FF phase, which borders at high temperatures to the 2SC phase. The critical temperature of phase transition from the 2SC to the unpaired state is in the range 20–30 MeV. We derive the equation of state of matter and its composition and show that matter in mature compact stars should be in the inhomogeneous FF-like superconducting state. We briefly discuss the astrophysical implications of such a phase in compact stars.
[Phys. Rev. D 82, 045029] Published Fri Aug 27, 2010
- Novel Interpretation of the “Θ^{+} (1540) Pentaquark” Peak
Author(s): A. Martínez Torres and E. Oset
We use a theoretical model of the γd→K^{+} K^{-} np reaction adapted to the experiment done at LEPS where a peak was observed and associated with the Θ^{+} (1540) pentaquark. The study shows that the method used in the experiment to assign momenta to the undetected proton and neutron, together with the chosen cuts, necessarily creates an artificial broad peak in the assumed K^{+} n invariant mass in the region of the claimed Θ^{+} (1540), such that the remaining strength seen for the experimental peak is compatible with a fluctuation of 2σ significance.
[Phys. Rev. Lett. 105, 092001] Published Thu Aug 26, 2010
- Acquiring information about neutrino parameters by detecting supernova neutrinos
Author(s): Ming-Yang Huang, Xin-Heng Guo, and Bing-Lin Young
We consider the supernova shock effects, the Mikheyev-Smirnov-Wolfenstein effects, the collective effects, and the Earth matter effects in the detection of type II supernova neutrinos on the Earth. It is found that the event number of supernova neutrinos depends on the neutrino mass hierarchy, the neutrino mixing angle θ_{13} , and neutrino masses. Therefore, we propose possible methods to identify the mass hierarchy and acquire information about θ_{13} and neutrino masses by detecting supernova neutrinos. We apply these methods to some current neutrino experiments.
[Phys. Rev. D 82, 033011] Published Thu Aug 19, 2010
- Very-high-energy gamma-ray signal from nuclear photodisintegration as a probe of extragalactic sources of ultrahigh-energy nuclei
Author(s): Kohta Murase and John F. Beacom
It is crucial to identify the ultrahigh-energy cosmic-ray sources and probe their unknown properties. Recent results from the Pierre Auger Observatory favor a heavy nuclear composition for the ultrahigh-energy cosmic rays. Under the requirement that heavy nuclei survive in these sources, using gamma-ray bursts as an example, we predict a diagnostic gamma-ray signal, unique to nuclei—the emission of deexcitation gamma rays following photodisintegration. These gamma rays, boosted from MeV to TeV-PeV energies, may be detectable by gamma-ray telescopes such as VERITAS, HESS, and MAGIC, and especially the next-generation CTA and AGIS. They are a promising messenger to identify and study individual ultrahigh-energy nuclei accelerators.
[Phys. Rev. D 82, 043008] Published Thu Aug 19, 2010
- Tensor charges and form factors of SU(3) baryons in the self-consistent SU(3) chiral quark-soliton model
Author(s): Tim Ledwig, Antonio Silva, and Hyun-Chul Kim
We investigate the tensor form factors of the baryon octet within the framework of the chiral quark-soliton model, emphasizing those of the nucleon, taking linear 1/N_{c} rotational as well as linear m_{s} corrections into account, and applying the symmetry-conserving quantization. We explicitly calculate the tensor form factors H_{T}^{q} (Q^{2} ) corresponding to the generalized parton distributions H_{T} (x,ξ,t). The tensor form factors are obtained for the momentum transfer up to Q^{2} ≤1 GeV^{2} and at a renormalization scale of 0.36 GeV^{2} . We find for the tensor charges δu=1.08, δd=-0.32, and δs=-0.01 and discuss their physical consequences, comparing them with those from other models. Results for tensor charges for the baryon octet are also given.
[Phys. Rev. D 82, 034022] Published Tue Aug 17, 2010
- Regularity-Induced Separation of Intrinsic and Collective Dynamics
Author(s): Michal Macek, Jan Dobeš, Pavel Stránský, and Pavel Cejnar
We propose that the adiabatic separation of collective and intrinsic motions in many-body systems is related to increased regularity of the intrinsic dynamics. The surmise is verified on the separation of rotations from intrinsic vibrations in the interacting boson model of nuclear structure.
[Phys. Rev. Lett. 105, 072503] Published Fri Aug 13, 2010
- Chiral condensate and dressed Polyakov loop in the Nambu–Jona-Lasinio model
Author(s): Tamal K. Mukherjee, Huan Chen, and Mei Huang
We investigate the chiral condensate and the dressed Polyakov loop or dual chiral condensate at finite temperature and density in the two-flavor Nambu–Jona-Lasinio model. The dressed Polyakov loop is regarded as an equivalent order parameter of deconfinement phase transition in a confining theory. We find the behavior of a dressed Polyakov loop in the absence of any confinement mechanism quite interesting. With only quark degrees of freedom present, it still shows an order parameter like behavior. It is found that in the chiral limit, the critical temperature for chiral phase transition coincides with that of the dressed Polyakov loop in the whole (T,μ) plane. In the case of explicit chiral symmetry breaking, it is found that the transition temperature for chiral restoration T_{c}^{χ} is smaller than that of the dressed Polyakov loop T_{c}^{D} in the low baryon density region where the transition is a crossover. With the increase of the current quark mass the difference between the two transition temperatures is found to be increasing. However, the two critical temperatures coincide in the high baryon density region where the phase transition is of first order. We give an explanation on the feature of T_{c}^{χ} =T_{c}^{D} in the case of 1st and 2nd order phase transitions, and T_{c}^{χ} [Phys. Rev. D 82, 034015] Published Fri Aug 13, 2010
- Spin-down of neutron stars by neutrino emission
Author(s): Maxim Dvornikov and Claudio Dib
We study the spin-down of a neutron star during its early stages due to the neutrino emission. The mechanism we consider is the subsequent collisions of the produced neutrinos with the outer shells of the star. We find that this mechanism can indeed slow down the star rotation but only in the first tens of seconds of the core formation, which is when the appropriate conditions of flux and collision rate are met. We find that this mechanism can extract less than 1% of the star angular momentum, a result which is much less than previously estimated by other authors.
[Phys. Rev. D 82, 043006] Published Fri Aug 13, 2010
- Polarization Transfer in the ^{4} He(e [over →] ,e^{′} p [over →] ) ^{3} H Reaction at Q^{2} =0.8 and 1.3 (GeV/c)^{2}
Author(s): M. Paolone et al. (E03-104 Collaboration)
Proton recoil polarization was measured in the quasielastic ^{4} He(e [over →] ,e^{′} p [over →] ) ^{3} H reaction at Q^{2} =0.8 and 1.3 (GeV/c)^{2} with unprecedented precision. The polarization-transfer coefficients are found to differ from those of the ^{1} H(e [over →] ,e^{′} p [over →] ) reaction, contradicting a relativistic distorted-wave approximation and favoring either the inclusion of medium-modified proton form factors predicted by the quark-meson coupling model or a spin-dependent charge-exchange final-state interaction. For the first time, the polarization-transfer ratio is studied as a function of the virtuality of the proton.
[Phys. Rev. Lett. 105, 072001] Published Thu Aug 12, 2010
- Midrapidity Antiproton-to-Proton Ratio in pp Collisons at sqrt[s] =0.9 and 7 TeV Measured by the ALICE Experiment
Author(s): K. Aamodt et al. (ALICE Collaboration)
The ratio of the yields of antiprotons to protons in pp collisions has been measured by the ALICE experiment at sqrt[s] =0.9 and 7 TeV during the initial running periods of the Large Hadron Collider. The measurement covers the transverse momentum interval 0.45[Phys. Rev. Lett. 105, 072002] Published Thu Aug 12, 2010
- Anomalous Fluctuations of s-Wave Reduced Neutron Widths of ^{192,194} Pt Resonances
Author(s): P. E. Koehler, F. Bečvář, M. Krtička, J. A. Harvey, and K. H. Guber
We obtained an unprecedentedly large number of s-wave neutron widths through R-matrix analysis of neutron cross-section measurements on enriched Pt samples. Careful analysis of these data rejects the validity of the Porter-Thomas distribution with a statistical significance of at least 99.997%.
[Phys. Rev. Lett. 105, 072502] Published Thu Aug 12, 2010
- Bounding W-W^{′} Mixing with Spin Asymmetries at RHIC
Author(s): Daniël Boer and Wilco J. den Dunnen
The W boson can obtain a small right-handed coupling to quarks and leptons through mixing with a hypothetical W^{′} boson that appears in many extensions of the standard model. Measuring or even bounding this coupling to the light quarks is very challenging. Only one model independent bound on the absolute value of the complex mixing parameter has been obtained to date. Here we discuss a method sensitive to both the real and CP-violating imaginary parts of the coupling, independent of assumptions on the new physics, and demonstrate quantitatively the feasibility of its measurement at RHIC.
[Phys. Rev. Lett. 105, 071801] Published Tue Aug 10, 2010
- Conformal symmetry and light flavor baryon spectra
Author(s): M. Kirchbach and C. B. Compean
The degeneracy among parity pairs systematically observed in the N and Δ spectra is interpreted to hint on a possible conformal symmetry realization in the light flavor baryon sector in line with AdS_{5} /CFT_{4} . The case is made by showing that all the observed N and Δ resonances with masses below 2500 MeV distribute fairly well each over the first levels of a unitary representation of the conformal group, a representation that covers the spectrum of a quark-diquark system, placed directly on a conformally compactified Minkowski spacetime, R^{1} ⊗S^{3} , as approached from the AdS_{5} cone. The free geodesic motion on the S^{3} manifold is described by means of the scalar conformal equation there, which is of the Klein-Gordon–type. The equation is then gauged by the curved Coulomb potential that has the form of a cotangent function. Conformal symmetry is not exact, this because the gauge potential slightly modifies the conformal centrifugal barrier of the free geodesic motion. Thanks to this, the degeneracy between P_{11} -S_{11} pairs from same level is relaxed, while the remaining states belonging to same level remain practically degenerate. The model describes the correct mass ordering in the P_{11} -S_{11} pairs through the spectra as a combined effect of the above conformal symmetry breaking, on the one side, and a parity change of the diquark from a scalar at low masses, to a pseudoscalar at higher masses, on the other. The quality of the wave functions is illustrated by calculations of realistic mean square charge radii and electric charge form factors on the examples of the proton, and the protonic P_{11} (1440), and S_{11} (1535) resonances. The scheme also allows for a prediction of the dressing function of an effective instantaneous gluon propagator from the Fourier transform of the gauge potential. We find a dressing function that is finite in the infrared and tends to zero at infinity.
[Phys. Rev. D 82, 034008] Published Tue Aug 10, 2010
- New analysis of the single transverse-spin asymmetry for hadron production at RHIC
Author(s): Koichi Kanazawa and Yuji Koike
We analyze the single transverse-spin asymmetry (SSAs) for inclusive hadron production in the pp collision at RHIC based on the twist-3 mechanism in QCD. As an origin of SSAs, we take into account of all kinds of pole contributions associated with the twist-3 quark-gluon correlation functions in the polarized proton. By the inclusion of the soft-fermion-pole contribution in addition to the soft-gluon-pole contribution, we find SSAs observed at RHIC are better described for all kinds of mesons. P_{T} dependence of the asymmetry and the comparison with the FNAL data are also presented.
[Phys. Rev. D 82, 034009] Published Tue Aug 10, 2010
- Power counting regime of chiral effective field theory and beyond
Author(s): J. M. M. Hall, D. B. Leinweber, and R. D. Young
Chiral effective field theory (χEFT) complements numerical simulations of quantum chromodynamics (QCD) on a space-time lattice. It provides a model-independent formalism for connecting lattice simulation results at finite volume and a variety of quark masses to the physical world. The asymptotic nature of the chiral expansion places the focus on the first few terms of the expansion. Thus, knowledge of the power-counting regime (PCR) of χEFT, where higher-order terms of the expansion may be regarded as negligible, is as important as knowledge of the expansion itself. Through the consideration of a variety of renormalization schemes and associated parameters, techniques to identify the PCR where results are independent of the renormalization scheme are established. The nucleon mass is considered as a benchmark for illustrating this general approach. Because the PCR is small, the numerical simulation results are also examined to search for the possible presence of an intrinsic scale which may be used in a nonperturbative manner to describe lattice simulation results outside of the PCR. Positive results that improve on the current optimistic application of chiral perturbation theory (χPT) beyond the PCR are reported.
[Phys. Rev. D 82, 034010] Published Tue Aug 10, 2010
- Effect of the Tensor Force on the Charge Exchange Spin-Dipole Excitations of ^{208} Pb
Author(s): C. L. Bai, H. Q. Zhang, H. Sagawa, X. Z. Zhang, G. Colò, and F. R. Xu
The charge exchange spin-dipole (SD) excitations of ^{208} Pb are studied by using a fully self-consistent Skyrme Hartree-Fock plus random phase approximation formalism which includes the tensor interaction. It is found, for the first time, that the tensor correlations have a unique, multipole-dependent effect on the SD excitations; that is, they produce a softening of 1^{-} states, but a hardening of 0^{-} and 2^{-} states. This paves the way to a clear assessment of the strength of the tensor terms. We compare our results with a recent measurement, showing that our choice of tensor terms improves the agreement with experiment. The robustness of our results is supported by the analytic form of the tensor matrix elements.
[Phys. Rev. Lett. 105, 072501] Published Mon Aug 09, 2010
- Finite volume effects for nucleon and heavy meson masses
Author(s): Gilberto Colangelo, Andreas Fuhrer, and Stefan Lanz
We apply the resummed version of the Lüscher formula to analyze finite volume corrections to the mass of the nucleon and of heavy mesons. We show that by applying the subthreshold expansion of the scattering amplitudes one can express the finite volume corrections in terms of only a few physical observables and the size of the box. In the case of the nucleon, the available information about the quark mass dependence of these physical quantities is discussed and used to assess the finite volume corrections to the nucleon mass as a function of the quark mass including a detailed analysis of the remaining uncertainties. For heavy mesons, the Lüscher formula is derived both fully relativistically and in a nonrelativistic approximation and a first attempt at a numerical analysis is made.
[Phys. Rev. D 82, 034506] Published Mon Aug 09, 2010
- Quantum phase transitions in the shapes of atomic nuclei
Author(s): Pavel Cejnar, Jan Jolie, and Richard F. Casten
Signatures of criticality in the evolution of the nuclear ground-state shapes across the N×Z plane are discussed. Attention is paid to specific data indicating sudden structural changes in various isotopic and isotonic chains of medium-mass and heavy even-even nuclei, as well as to diverse theoretical aspects of the models used to describe these changes. The interacting boson model and the geometric collective model, in particular, are discussed in detail, the former providing global predictions for the evolution of collective observables in nuclei between closed shells and the latter yielding a parameter-efficient description of nuclei at the critical points of shape transitions. Some issues related to the mechanism of first- and second-order quantum phase transitions in general many-body systems are also outlined.
[Rev. Mod. Phys. 82, 2155] Published Thu Aug 05, 2010
- Neutrino mixing with broken S_{3} symmetry
Author(s): Duane A. Dicus, Shao-Feng Ge, and Wayne W. Repko
We explore the consequences of assuming that the neutrino mass matrix is a linear combination of the matrices of a three-dimensional representation of the group S_{3} and that it has one zero mass eigenvalue. When implemented, these two assumptions allow us to express the transformation matrix relating the mass eigenstates to the flavor eigenstates in terms of a single parameter which we fit to the available data.
[Phys. Rev. D 82, 033005] Published Thu Aug 05, 2010
- Measurement of the solar ^{8} B neutrino rate with a liquid scintillator target and 3 MeV energy threshold in the Borexino detector
Author(s): G. Bellini et al. (Borexino Collaboration)
We report the measurement of ν-e elastic scattering from ^{8} B solar neutrinos with 3 MeV energy threshold by the Borexino detector in Gran Sasso (Italy). The rate of solar neutrino-induced electron scattering events above this energy in Borexino is 0.22±0.04(stat)±0.01(syst) cpd/100 t, which corresponds to Φ_{ ^{8} B}^{ES} =2.4±0.4±0.1×10^{6} cm^{-2} s^{-1} , in good agreement with measurements from SNO and SuperKamiokaNDE. Assuming the ^{8} B neutrino flux predicted by the high metallicity standard solar model, the average ^{8} B ν_{e} survival probability above 3 MeV is measured to be 0.29±0.10. The survival probabilities for ^{7} Be and ^{8} B neutrinos as measured by Borexino differ by 1.9σ. These results are consistent with the prediction of the MSW-LMA solution of a transition in the solar ν_{e} survival probability P_{ee} between the low-energy vacuum-driven and the high-energy matter-enhanced solar neutrino oscillation regimes.
[Phys. Rev. D 82, 033006] Published Thu Aug 05, 2010
- Elliptic and Hexadecapole Flow of Charged Hadrons in Au+Au Collisions at sqrt[s_{NN} ] =200 GeV
Author(s): A. Adare et al. (PHENIX Collaboration)
Differential measurements of the elliptic (v_{2} ) and hexadecapole (v_{4} ) Fourier flow coefficients are reported for charged hadrons as a function of transverse momentum (p_{T} ) and collision centrality or number of participant nucleons (N_{part} ) for Au+Au collisions at sqrt[s_{NN} ] =200 GeV. The v_{2,4} measurements at pseudorapidity |η|≤0.35, obtained with four separate reaction-plane detectors positioned in the range 1.0<|η|<3.9, show good agreement, indicating the absence of significant Δη-dependent nonflow correlations. Sizable values for v_{4} (p_{T} ) are observed with a ratio v_{4} (p_{T} ,N_{part} )/v_{2}^{2} (p_{T} ,N_{part} )≈0.8 for 50≲N_{part} ≲200, which is compatible with the combined effects of a finite viscosity and initial eccentricity fluctuations. For N_{part} ≳200 this ratio increases up to 1.7 in the most central collisions.
[Phys. Rev. Lett. 105, 062301] Published Wed Aug 04, 2010
- Weak kaon production off the nucleon
Author(s): M. Rafi Alam, I. Ruiz Simo, M. Sajjad Athar, and M. J. Vicente Vacas
The weak kaon production off the nucleon induced by neutrinos is studied at the low and intermediate energies of interest for some ongoing and future neutrino oscillation experiments. This process is also potentially important for the analysis of proton decay experiments. We develop a microscopical model based on the SU(3) chiral Lagrangians. The basic parameters of the model are f_{π} , the pion decay constant, Cabibbo’s angle, the proton and neutron magnetic moments, and the axial vector coupling constants for the baryons octet, D and F, that are obtained from the analysis of the semileptonic decays of neutron and hyperons. The studied mechanisms are the main source of kaon production for neutrino energies up to 1.2 to 1.5 GeV for the various channels and the cross sections are large enough to be amenable to be measured by experiments such as Minerva and T2K.
[Phys. Rev. D 82, 033001] Published Wed Aug 04, 2010
- Nonuniversality of Transverse Momentum Dependent Parton Distributions at Small x
Author(s): Bo-Wen Xiao and Feng Yuan
We study the universality issue of the transverse momentum dependent parton distributions at small x, by comparing the initial and final state interaction effects in di-jet-correlations in pA collisions with those in deep inelastic lepton-nucleus scattering. We demonstrate the nonuniversality by performing an explicit calculation in a particular model where the multiple gauge boson exchange contributions are summed up to all orders. We comment on the implications of our results on the theoretical interpretation of dihadron correlation in dA collisions in terms of the saturation phenomena in deep inelastic lepton-nucleus scattering.
[Phys. Rev. Lett. 105, 062001] Published Mon Aug 02, 2010
- QCD critical point in a quasiparticle model
Author(s): P. K. Srivastava, S. K. Tiwari, and C. P. Singh
Recent theoretical investigations have unveiled a rich structure in the quantum chromodynamics phase diagram, which consists of quark-gluon plasma and the hadronic phases but also supports the existence of a crossover transition ending at a critical end point (CEP). We find a too large variation in the determination of the coordinates of the CEP in the temperature (T) baryon chemical potential (μ_{B} ) plane; and, therefore, its identification in the current heavy-ion experiments becomes debatable. Here we use an equation of state for a deconfined quark-gluon plasma using a thermodynamically-consistent quasiparticle model involving noninteracting quarks and gluons having thermal masses. We further use a thermodynamically-consistent excluded-volume model for the hadron gas, which was recently proposed by us. Using these equations of state, a first-order deconfining phase transition is constructed using Gibbs’s criteria. This leads to an interesting finding that the phase transition line ends at a critical end point (CEP) beyond which a crossover region exists. Using our thermal hadron gas model, we obtain a chemical freeze out curve, and we find that the CEP lies in close proximity to this curve as proposed by some authors. The coordinates of CEP are found to lie within the reach of Relativistic heavy-ion collider experiment.
[Phys. Rev. D 82, 014023] Published Fri Jul 30, 2010
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