119304973
Nuclear suppression of azimuthal asymmetries in semi-inclusive deep inelastic scattering off polarized targets
We extend the study of nuclear dependence of the transverse momentum dependent parton distribution functions and azimuthal asymmetries to semi-inclusive deep inelastic scattering (SIDIS) off polarized nuclear targets. We show that azimuthal asymmetries are suppressed for SIDIS off a polarized nuclear target relative to that off a polarized nucleon due to multiple scattering inside the nucleus. Using the value of transport parameter inside large nuclei extracted from jet quenching analyses in SIDIS off nuclear targets, we also present a numerical estimate of the nuclear suppression of the azimuthal asymmetry that might be useful to guide the future experimental studies of SIDIS off polarized nuclear targets.
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.
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.
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.
126140598
Report of the RHIC Workshop p + A subgroup
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.
121654775
The possible effect of scalar meson on the symmetry energy curve in the viewpoint of the quark-meson-coupling model
We give the energy density functional of quark-meson-coupling model within the Hartree-Fock approximation and make comparison with relativistic-mean-field and Skyrme-Hartree-Fock models. We find that the discrepancy of these models is mainly from the isovector channel of the energy density functional, which is also the major cause of different descriptions of symmetry energy against density. In the viewpoint of quark-meson-coupling model, the scalar meson through Fock exchange makes a density dependent form of the isovector channel which can soften the symmetry energy curve.
119185233
Study on the temperature dependence of BGO light yield
The temperature dependence of BGO coupled with photomultiplier tube R5610A-01 was studied in the range of −30–30°C. The temperature coefficient of the BGO and R5610A as a whole was tested to be −1.82%/°C. And the temperature coefficient of the gain of the R5610A is −0.44%/°C which was tested in the same situation using a blue LED. Thus the temperature coefficient of BGO’s light yield can be evaluated as −1.38%/°C.
14667078
Study of the single neutral top pion production process at {gamma}{gamma} collider
{gamma}{gamma}{yields}{pi}{sub t}{sup 0} is the major production mechanism of the neutral top pion at the linear colliders. In this paper, we calculate the cross section of the process {gamma}{gamma}{yields}{pi}{sub t}{sup 0} and discuss the potential to observe the neutral top pion via its various decay modes at the planned International Linear Collider. The study shows that, among the various neutral top-pion production processes at the linear colliders, the cross section of {gamma}{gamma}{yields}{pi}{sub t}{sup 0} is the largest one which can reach the level of 10{sup 1}-10{sup 2} fb. Because of the existence of the tree-level flavor-changing coupling {pi}{sub t}{sup 0}tc, {gamma}{gamma}{yields}{pi}{sub t}{sup 0}{yields}tc can provide enough number of typical signals to identify the neutral top pion with the clean SM background. Therefore, the process {gamma}{gamma}{yields}{pi}{sub t}{sup 0} plays an important role in searching for the neutral top pion and tests the TC2 model.
120209602
Longitudinal Double Spin Asymmetries in Heavy Flavor Production in Polarized p+p Collisions at s = 200 GeV
One of the main goals of the RHIC spin program is to determine the contribution of gluons to the proton spin. At RHIC energies, heavy quark (charm and beauty) production is expected to be dominated by gluon‐gluon interactions, so a measurement of the double longitudinal spin asymmetry ALL in heavy quark production in polarized p+p collisions directly probes the polarized gluon distribution inside the proton. We present the latest results on an ALL measurement for J/Ψ and open charm production measured by the PHENIX detector.
15351369
Charm production in deep inelastic scattering from threshold to high Q2
Charm final states in deep inelastic scattering constitute ~ 25% of the inclusive cross-section at small x as measured at HERA. These data can reveal important information on the charm and gluon structure of the nucleon if they are interpreted in a consistent perturbative QCD framework which is valid over the entire energy range from threshold to the high energy limit. We describe in detail how this can be carried out order-by-order in PQCD in the generalized MSbar formalism of Collins (generally known as the ACOT approach), and demonstrate the inherent smooth transition from the 3-flavor to the 4-flavor scheme in a complete order αs calculation, using a Monte Carlo implementation of this formalism. This calculation is accurate to the same order as the conventional NLO F2 calculation in the limit Q/mc >> 1. It includes the resummed large logarithm contributions of the 3-flavor scheme (generally known in this context as the fixed-flavor-number or FFN scheme) to all orders of αsln (mc2/Q2). For the inclusive structure function, comparison with recent HERA data and the existing FFN calculation reveals that the relatively simple order-αs (NLO) 4-flavor (mc≠0) calculation can, in practice, be extended to rather low energy scales, yielding good agreement with data over the full measured Q2 range. The Monte Carlo implementation also allows the calculation of differential distributions with relevant kinematic cuts. Comparisons with available HERA data show qualitative agreement; however, they also indicate the need to extend the calculation to the next order to obtain better description of the differential distributions.