16258194
Energy loss effects on charm and bottom production in high-energy heavy-ion collisions
We study the effect of energy loss on charm and bottom quarks in high-energy heavy-ion collisions including longitudinal expansion and partial thermalization. We find that high-p{sub {perpendicular}} heavy quarks are greatly suppressed, and consequently, high-mass dileptons from heavy quark decays are also suppressed. We consider in detail the detector geometry and single lepton energy cuts of the PHENIX detector at the Relativistic Heavy Ion Collider. Because of the longitudinal expansion, the suppressions of ee, e{mu}, and {mu}{mu} pairs resulting from the heavy quark energy loss are very different due to the different rapidity coverages and energy cuts. The assumed energy loss rate, on the order of 1 GeV/fm, results in a large suppression on dielectrons, and dielectrons from heavy quark decays become comparable or even lower than the Drell-Yan yield. It is thus possible to probe the energy loss rate of the medium using dileptons from heavy quark decays. {copyright} {ital 1998} {ital The American Physical Society}
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
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.
119228671
The flavor-changing single-top quark production in the littlest Higgs model with T parity at the LHC
Abstract The littlest Higgs model with discrete symmetry named “T-parity” (LHT) is an interesting new physics model which does not suffer strong constraints from electroweak precision data. One of the important features of the LHT model is the existence of new source of FC interactions between the SM fermions and the mirror fermions. These FC interactions can make significant loop-level contributions to the couplings tcV , and furthermore enhance the cross sections of the FC single-top quark production processes. In this paper, we study some FC single-top quark production processes, p p → t c ¯ and p p → t V , at the LHC in the LHT model. We find that the cross sections of these processes strongly depend on the mirror quark masses. The processes p p → t c ¯ and p p → t g have large cross sections with heavy mirror quarks. The observation of these FC processes at the LHC is certainly the clue of new physics, and further precise measurements of the cross sections can provide useful information about the free parameters in the LHT model, specially about the mirror quark masses.
119042314
CHARM PRODUCTION AT LARGE RAPIDITIES IN p+p AND d+Au COLLISIONS AT PHENIX AT RHIC
We study charm production through dimuon and single muon measurements at forward and backward rapidities in p+p and d+Au collisions with the PHENIX muon detectors. We also compare open charm to $J/\psi$ yields in the forward and backward rapidities in d+Au collisions and study the origin of the large forward and backward asymmetry in open charm production observed by the PHENIX experiment.
73648727
Polarization control proposal for Shanghai deep ultraviolet free electron laser
In this paper, a fully coherent radiation option with controllable polarization is proposed for the Shanghai deep ultraviolet free electron laser (FEL) test facility. Intensive start-to-end simulation suggests that the two crossed planar undulators which generate the horizontal and vertical linear polarized FEL, should be placed as close as possible for avoiding the polarization performance degradation of the final combined FEL radiation. With the existence of the phase-shifter between the two crossed radiators. Fourier-Transform-Limited output radiation with 100 nJ order pulse energy, 5 Ps full pulse length and circular polarization degree above 90% could be achieved. (C) 2012 Elsevier B.V. All rights reserved.
122096987
ASSOCIATED PRODUCTION OF SINGLE HEAVY T-QUARK IN THE LEFT–RIGHT TWIN HIGGS MODEL AT THE LHC
The heavy T-quark is one of the most crucial ingredients in the left–right twin Higgs model, which is introduced to cancel the largest contribution of the Standard Model top quark to the Higgs boson mass at one-loop level. In this paper, we study the relevant single heavy T-quark production processes, the 2 → 2 partonic processes of qb → q'T and , the 2 → 3 partonic processes of and at the CERN LHC. Our numerical results show that the 2 → 3 process can be quite important, as its cross-section is about 60% of that for the 2 → 2 process at the LHC. We also show the pT distribution and the rapidity distributions for out-going particles. For the 2 → 3 process, the production rate of the final state can be larger than 100 fb with reasonable values of the free parameters. The possible signatures of the heavy T-quark might be detected via the process at the LHC.
15239653
Probing the topcolor-assisted technicolor model via the single t-quark production at the CERN LHC
The single t-quark production in proton-proton collisions can proceed through three distinct processes: tq, tb, tW productions. With the running of the Large Hadron Collider (LHC) at CERN, it has good potential to measure each single t-quark production mode. The topcolor-assisted technicolor (TC2) model, one of the promising dynamical theories, predicts some new particles at the several hundred GeV scale: three top-pion bosons ({pi}{sub t}{sup {+-}}, {pi}{sub t}{sup 0}) and one top-Higgs boson (h{sub t}). These particles are regarded as the typical feature of the TC2 model and can contribute to some processes. In this paper, we systematically study the contribution of the TC2 model to the single t-quark production at the Hadron colliders, especially at the LHC. The TC2 model can contribute to the cross section of the single t-quark production in two different ways. First, the existence of the top pions and top Higgs can modify the Wtb coupling via their loop contributions, and such modification can cause the correction to the cross sections of all three production modes. Our study shows that this kind of correction is negative and very small in all cases. Thus it is difficult to observe such a correction even at the LHC.more » On the other hand, there exist the tree-level flavor-changing (FC) couplings in the TC2 model which can also contribute to the cross sections of the tq and tb production processes. The resonant effect can greatly enhance the cross sections of the tq and tb productions. The first evidence of the single t-quark production has been reported by the D0 collaboration and the measured cross section for the single t-quark production of {sigma}(pp{yields}tb+X,tqb+X) is compatible at the 10% level with the standard model prediction. Because the light top pion can make a great contribution to the tb production, the top-pion mass should be very large in order to make the predicted cross section in the TC2 model be consistent with the Tevatron experiments. More detailed information about the top-pion mass and the FC couplings in the TC2 model should be obtained with the running of the LHC.« less