14560383
Charmonium production from hot hadronic matter
Abstract Charmonium production from D D annihilation in the hadron gas formed in ultra-relativistic heavy-ion collisions is studied. With initial conditions taken from the HIJING parton model, we have estimated the number of J / ψ produced from an expanding hadron gas, using the J / ψ absorption and production cross sections obtained from either an effective Lagrangian or the quark-exchange model. We find that J / ψ production is negligible in heavy-ion collisions at the Relativistic Heavy Ion Collider (RHIC) but may be important at the Large Hadron Collider (LHC), where more charm mesons are produced. Similar results are obtained for ψ ′ production from the hadron gas at RHIC and LHC.
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.
126140598
Report of the RHIC Workshop p + A subgroup
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.
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.
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.
120703041
PAIR PRODUCTION OF CHARGED TOP-PIONS ASSOCIATED WITH Z GAUGE BOSON IN THE TOPCOLOR-ASSISTED TECHNICOLOR MODEL AT THE ILC
The top-pions are the three additional typical particles predicted by the topcolor-assisted technicolor (TC2) model and the observation of these particles can be regarded as the direct evidence of the TC2 model. In this paper, we investigate the production of a pair of charged top-pions associated with Z gauge boson at the International Linear Collider (ILC), i.e. and . We calculate the production rate of the process and present the distributions of the transverse momenta of Z gauge boson and charged top-pion . We find that the cross-section of the process can reach 1 fb with reasonable parameter space of the TC2 model. Considering the main decay mode of charged top-pion, we find that such a production may provide copious events. While the cross-section of the process is below 1 fb, hence the process will play an important role in the test of the TC2 model at the ILC when compared with the process .
13970711
Higgs boson pair production process e+ e- ---> ZHH in the littlest Higgs model at the ILC
In this paper, we calculate the contribution of the littlest Higgs (LH) model to the process e+e− → ZHH at the future high energy e+e− collider (ILC). The results show that, within the parameter spaces preferred by the electroweak precision, the deviation of the total cross sections from its SM value varies from a few per cent to tens of per cent. The correction of the LH model to the process might be detected at the future ILC experiments in the favourable parameter space. On the other hand, we find that the correction of the LH model is sensitive to the trilinear Higgs coupling in some case and the process can also provide us a chance to probe such coupling in the LH model.
38524395
Simulation studies of Micromegas and parallel ionization multiplier with woven mesh
We report simulation results of the Micromegas in a bulk and PIM (parallel ionization multiplier) with one or more layers of woven micromeshes based on 3D models and Garfield/ Magboltz. Studies are conducted for different detector geometries. Effects of wire diameter, mesh pitch, mesh effective thickness and gas mixture are investigated. The transverse diffusion of drifting electrons and broadening of electron clouds that affect electron transfer through the micromeshes are studied. Different arrangements of gas gains in the required avalanche and signal induction regions of a PIM-like configuration are studied. The motivation of this work is to understand the electron transfer process in Micromegas and PIMs constructed by using relatively thick woven micromeshes. We have attempted to find optimized PIM configurations in order to obtain high gas gain, fast rise time and other desirable detector properties.
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.