119238692
Effect of longitudinal fluctuation in event-by-event (3+1)D hydrodynamics
Abstract Hadron spectra and elliptic flow in relativistic heavy-ion collisions are studied in event-by-event (3+1)D ideal hydrodynamic simulations with fluctuating initial conditions given by the AMPT Monte Carlo model. Both the coherent soft gluon production from wounded nucleons and incoherent mini-jet production in semi-hard parton scatterings are considered. These partons take part in parton cascade and are assumed to be locally thermalized. They provide the fluctuating initial conditions for hydrodynamic simulations with a Gaussian smearing. Effects of both transverse and longitudinal fluctuations are studied. The initial fluctuations along rapidity direction lead to expanding hot spots in longitudinal direction, which will reduce elliptic flow and the yield of particles at high transverse momentum. The intrinsic correlation introduced in the fluctuating initial conditions is also found to influence the di-hadron correlation of the final hadrons.
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.
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.
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.
124732549
Beam emittance investigation in high brightness injector using different driver laser profiles
Beam emittance plays an important role in any accelerator, and it is a main parameter to judge the performance of an accelerator. Emittance optimization is an indispensable part in conditioning and operation of the facility. For a laser-driven high brightness injector, different time structure of the laser pulse has different effects on transverse emittance. In order to compare Gaussian and flat-top laser pulse, systematic simulations of 500 pC have been done. From the simulation results, one can see that flat-top pulse laser will yield smaller minimal transverse beam size and transverse beam emittance than Gaussian pulse laser.
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.
118425985
Spatial anisotropy: a method to study anisotropic flow in heavy ion collisions
We introduce a method to study anisotropic flow parameter vn as a collective probe to Quark Gluon Plasma in relativistic heavy ion collisions. The emphasis is put on the use of the Fourier expansion of initial spatial azimuthal distributions of participant nucleons in the overlapped region. The coefficients n of Fourier expansion are called the spatial anisotropy parameter for the n-th harmonic. We propose that collective dynamics can be studied by vn/n. In this paper, we will discuss in particular the second (n = 2) and the fourth (n = 4) harmonics.
118479131
Venus transit, aureole and solar diameter
The possibility to measure the solar diameter using the transits of Mercury has been exploited to investigate the past three centuries of its evolution and to calibrate these measurements made with satellites. This measurement basically consists to compare the ephemerides of the internal contact timings with the observed timings. The transits of Venus of 2004 and 2012 gave the possibility to apply this method, involving a planet with atmosphere, with the refraction of solar light through it creating a luminous arc all around the disk of the planet. The observations of the 2012 transit made to measure the solar diameter participate to the project Venus Twilight Experiment to study the aureole appearing around it near the ingress/egress phases.
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.