120366134
Discovery of Jet Quenching and Beyond
Recent observation of high-pT hadron spectra suppression and mono-jet production in central Au+Au collisions and their absence in d+Au collisions at RHIC have confirmed the long predicted phenomenon of jet quenching in high-energy heavy-ion collisions. Detailed analyses of the experimental data also show parton energy loss as the mechanism for the discovered jet quenching. Using a pQCD parton model that incorporates medium modified parton fragmentation functions and comparing to experimental data from deeply inelastic scattering off nuclei, one can conclude that the initial gluon (energy) density of the hot matter produced in central Au+Au collisions that causes jet quenching at RHIC is about 30 (100) times higher than in a cold Au nucleus. Combined with data on bulk and collective properties of the hot matter, the observed jet quenching provides strong evidence for the formation of a strongly interacting quark–gluon plasma in central Au+Au collisions at RHIC.
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.
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.
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.
120048813
A criterion for the order of QGP phase transition
Based on the extended Ginzburg-Landau model, it is shown that the dependences of the scaled factorial moments ln Fq on phase space intervals are different for first- and second-order QGP phase transitions. When ln Fq are fitted to polynomials of X ≡ δ13, the relative sign between the fitted coefficients can be used to judge the order of phase transitions.
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.
20087962
Research on DC-clearing electric field and changes of focusing structure parameters of storage ring
This paper presents DC clearing field to clear ions in vacuum pipe of Hefei ring. It also presents changes of focusing structure parameters caused by the clearing field. It concludes that tune shifts caused by the field are related to real-time closed orbit of the beam. The paper points out that the field asymmetrically distributed along the ring destroys the symmetry of focusing structure and decreases the ring acceptance, which has negative effect to injection and accumulation process in certain condition.
54621041
Kanthal Alloy Based S-Band Collinear Load R and D for Linear Accelerators
Collinear load is a substitute for waveguide load to miniaturize irradiation accelerators and make the system compact. The key technology is to design coaxial cavities coated inside with attenuating materials which will terminate the remnant power, meanwhile the operation frequency of 2856 MHz retains. For lossy materials such as Kanthal (25%Cr-5%Al-Fe) alloy, CST is used to simulate the effect of the coating on the load cavity properties like the operation frequency and attenuation. The frequency shifts caused by the coatings would be compensated by the strategy of cavity dimensions adjustment. Simulations revealed the compensation rules of the cavity inner radius b. Meanwhile the relationship between the attenuation and the coating area was also resolved. Based on a specified power allocation, a 15 kW collinear load consisting of six cavities at 2π/3 mode was designed with one-way attenuation of -18.8 dB. Two sets of prototype cavities have been manufactured and the experiment results are presented, compared with the CST simulations.
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.