119510990
High pT hadron spectra in high-energy heavy-ion collisions
Abstract We calculate the hadron spectra in high-energy pp , pA and AA collisions within a pQCD parton model. Analyses of experimental data show that the modification of the spectra in pA and AA as compared to that in pp collisions is consistent with multiple parton scattering scenario and is dictated by the transition from absorptive soft interaction at low p T to incoherent hard parton scattering at high p T . This analysis not only sheds new light on the limits to the physics analysis based on thermal fire-ball models but also provides a more quantitative baseline results on which one can study the effects of parton energy loss in the hadron spectra at high p T .
119298211
Relics of Minijets amid Anisotropic Flows in High-energy Heavy-ion Collisions
Two dimensional low-$p_T$ dihadron correlations in azimuthal angle $\phi$ and pseudo-rapidity $\eta$ in high-energy heavy-ion collisions are investigated within both the HIJING Monte Carlo model and an event-by-event (3+1)D ideal hydrodynamic model. Without final-state interaction and collective expansion, dihadron correlations from HIJING simulations have a typical structure from minijets that contains a near-side two-dimensional peak and an away-side ridge along the $\eta$-direction. In contrast, event-by-event (3+1)D ideal hydrodynamic simulations with fluctuating initial conditions from the HIJING+AMPT model produce a strong dihadron correlation that has an away-side as well as a near-side ridge. Relics of intrinsic dihadron correlation from minijets in the initial conditions still remain as superimposed on the two ridges. By varying initial conditions from HIJING+AMPT, we study effects of minijets, non-vanishing initial flow and longitudinal fluctuation on the final state dihadron correlations. With a large rapidity gap, one can exclude near-side correlations from minijet relics and dihadron correlations can be described by the superposition of harmonic flows up to the 6th order. When long-range correlations with a large rapidity gap are subtracted from short-range correlations with a small rapidity gap, the remaining near-side dihadron correlations result solely from relics of minijets. Low transverse momentum hadron yields per trigger ($p_T^{\rm trig} <4$ GeV/$c$, $p_T^{\rm asso}<2$ GeV/$c$) in central heavy-ion collisions are significantly enhanced over that in p+p collisions while widths in azimuthal angle remain the same, in qualitative agreement with experimental data.
126140598
Report of the RHIC Workshop p + A subgroup
42468399
Berry curvature and four-dimensional monopoles in the relativistic chiral kinetic equation.
We derive a relativistic chiral kinetic equation with manifest Lorentz covariance from Wigner functions of spin-1/2 massless fermions in a constant background electromagnetic field. It contains vorticity terms and a four-dimensional Euclidean Berry monopole which gives an axial anomaly. By integrating out the zeroth component of the 4-momentum p, we reproduce the previous three-dimensional results derived from the Hamiltonian approach, together with the newly derived vorticity terms. The phase space continuity equation has an anomalous source term proportional to the product of electric and magnetic fields (FσρF[over ˜]σρ∼EσBσ). This provides a unified interpretation of the chiral magnetic and vortical effects, chiral anomaly, Berry curvature, and the Berry monopole in the framework of Wigner functions.
17734649
Probe initial parton density and formation time via jet quenching
Medium modification of jet fragmentation function due to multiple scattering and induced gluon radiation leads directly to jet quenching or suppression of leading particle distribution from jet fragmentation. One can extract an effective total parton energy loss which can be related to the total transverse momentum broadening. For an expanding medium, both are shown to be sensitive to the initial parton density and formation time. Therefore, one can extract the initial parton density and formation time from simultaneous measurements of parton energy loss and transverse momentum broadening. Implication of the recent experimental data on effects of detailed balance in parton energy loss is also discussed.
33523602
Role of multiple minijets in high-energy hadronic reactions.
The multiplicity distributions of charged particles in high-energy hadron collisions including the production of multiple minijets are considered in the framework of the eikonal formalism. Large-multiplicity events at high energies are found to be dominated by the production of many jets with 2{le}{ital P}{sub {ital T}}{le}4 GeV. The contributions from larger-{ital P}{sub {ital T}} minijets become prevailing for high-multiplicity fluctuations in narrow rapidity intervals.
37119712
Heavy Flavor Production at PHENIX at RHIC
A study of heavy flavor production in different collision systems in various kinematic regions presents an opportunity to probe cold nuclear medium and hot dense matter effects. Results from the PHENIX experiment on J/ψ and open charm production in Au+Au and Cu+Cu collisions at sNN =200 GeV are presented. The data show strong J/ψ suppression in central AA collisions, similar to NA50 results, and strong suppression in high pT open charm production. The J/ψ production in Au+Au and d+Au collisions is compared to understand the cold nuclear medium effects. The data show significant cold nuclear effects in charm production in d+Au collisions at forward and backward rapidity ranges.
118629382
Top quark rare three-body decays in the littlest Higgs model with T parity
In the littlest Higgs model with T-parity (LHT), the mirror quarks have flavor structures and will contribute to the top quark flavor changing neutral current. In this work, we perform an extensive investigation of the top quark rare three-body decays t{yields}cVV, (V={gamma}, Z, g) and t{yields}cff, (f=b, {tau}, {mu}, e) at one-loop level. Our results show that the branching ratios of t{yields}cgg and t{yields}cbb could reach O(10{sup -3}) in the favorite parameter space of the littlest Higgs model with T-parity, which implies that these decays may be detectable at the LHC or ILC, while for the other decays, their rates are too small to be observable at the present or future colliders.
118419759
Electromagnetic Contribution to the Proton-Neutron Mass Splitting
We study the electromagnetic contribution to the proton-neutron mass splitting by combining lattice simulations and the modified Cottingham sum rule of Walker-Loud, Carlson and Miller. This analysis yields an estimate of the isovector nucleon magnetic polarizability as a function of pion mass. The physical value, obtained by chiral extrapolation to the physical pion mass, is $\beta_{p-n}=(-1.12 \pm 0.40)\times 10^{-4}\ \mathrm{fm}^3$, which is in agreement with the empirical result, albeit with a somewhat smaller error. As a result, we find $\delta M^{\gamma}_{p-n}=1.04 \pm 0.11\ \mathrm{MeV}$, which represents a significant improvement in precision.
198138925
Oscillations of moments in high-energy nucleus-nucleus collisions
The definitions of density function and moment of multiplicity distribution are introduced, and the method of moment analysis in e+e- and proton-proton (pp) interactions is extended into nucleus-nucleus (AA) interactions. We analyze the data for relativistic nucleus-nucleus collisions and calculate the values of Hq for charged particle multiplicity distributions, by which we study systematically the dependences of Hqon incident energy, mass of colliding system, pseudorapidity interval, centrality and truncation of multiplicity. We compare the oscillation structures induced by e+ e-, pp and AA interactions, and the comparison and analysis are carried out between experimental data and QCD prediction. The latest results are given in this paper.
119206545
TYPE IIn SUPERNOVA SN 2010jl: OPTICAL OBSERVATIONS FOR OVER 500 DAYS AFTER EXPLOSION
We present extensive optical observations of a Type IIn supernova (SN IIn) 2010jl for the first 1.5 years after its discovery. The UBVRI light curves demonstrated an interesting two-stage evolution during the nebular phase, which almost flatten out after about 90 days from the optical maximum. SN 2010jl has one of the highest intrinsic Ha luminosities ever recorded for an SN IIn, especially at late phase, suggesting a strong interaction of SN ejecta with the dense circumstellar material (CSM) ejected by the progenitor. This is also indicated by the remarkably strong Balmer lines persisting in the optical spectra. One interesting spectral evolution about SN 2010jl is the appearance of asymmetry of the Balmer lines. These lines can be well decomposed into a narrow component and an intermediate-width component. The intermediate-width component showed a steady increase in both strength and blueshift with time until t similar to 400 days after maximum, but it became less blueshifted at t similar to 500 days, when the line profile appeared relatively symmetric again. Owing to the fact that a pure reddening effect will lead to a sudden decline of the light curves and a progressive blueshift of the spectral lines, we therefore propose that the asymmetric profiles of H lines seen in SN 2010jl are unlikely due to the extinction by newly formed dust inside the ejecta, contrary to the explanation by some early studies. Based on a simple CSM-interaction model, we speculate that the progenitor of SN 2010jl may suffer a gigantic mass loss (similar to 30-50 M-circle dot) a few decades before explosion. Considering a slow-moving stellar wind (e. g., similar to 28 km s(-1)) inferred for the preexisting, dense CSM shell and the extremely high mass-loss rate (1-2 M-circle dot yr(-1)), we suggest that the progenitor of SN 2010jl might have experienced a red supergiant stage and may explode finally as a post-red supergiant star with an initial mass above 30-40 M-circle dot.