arXiv subjects

M. S. Daugherity

Publications and source records attributed to M. S. Daugherity.

96 records · Page 6Linked to original sources

arXiv2014

Comparison of the space-time extent of the emission source in $d$$+$Au and Au$+$Au collisions at $\sqrt{s_{NN}}=200$ GeV

Two-pion interferometry measurements in $d$$+$Au and Au$+$Au collisions at $\sqrt{s_{NN}}=200$ GeV are used to extract and compare the Gaussian source radii R$_{\rm out}$, R$_{\rm side}$, and R$_{\rm long}$, which characterize the space-time extent of the emission sources. The comparisons, which are performed as a function of collision centrality and the mean transverse momentum for pion pairs, indicate strikingly similar patterns for the $d$$+$Au and Au$+$Au systems. They also indicate a linear dependence of R$_{\rm side}$ on the initial transverse geometric size $\bar{R}$, as well as a smaller freeze-out size for the $d$$+$Au system. These patterns point to the important role of final-state rescattering effects in the reaction dynamics of $d$$+$Au collisions.

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arXiv2014

Nuclear matter effects on $J/ψ$ production in asymmetric Cu+Au collisions at $\sqrt{s_{_{NN}}}$ = 200 GeV

We report on $J/ψ$ production from asymmetric Cu+Au heavy-ion collisions at $\sqrt{s_{_{NN}}}$=200 GeV at the Relativistic Heavy Ion Collider at both forward (Cu-going direction) and backward (Au-going direction) rapidities. The nuclear modification of $J/ψ$ yields in Cu$+$Au collisions in the Au-going direction is found to be comparable to that in Au$+$Au collisions when plotted as a function of the number of participating nucleons. In the Cu-going direction, $J/ψ$ production shows a stronger suppression. This difference is comparable in magnitude and has the same sign as the difference expected from shadowing effects due to stronger low-$x$ gluon suppression in the larger Au nucleus. The relative suppression is opposite to that expected from hot nuclear matter dissociation, since a higher energy density is expected in the Au-going direction.

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arXiv2014

Concept for an Electron Ion Collider (EIC) detector built around the BaBar solenoid

The PHENIX collaboration presents here a concept for a detector at a future Electron Ion Collider (EIC). The EIC detector proposed here, referred to as ePHENIX, will have excellent performance for a broad range of exciting EIC physics measurements, providing powerful investigations not currently available that will dramatically advance our understanding of how quantum chromodynamics binds the proton and forms nuclear matter.

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arXiv2012

Medium modification of jet fragmentation in Au+Au collisions at sqrt(s_NN)=200 GeV measured in direct photon-hadron correlations

The jet fragmentation function is measured with direct photon-hadron correlations in p+p and Au+Au collisions at sqrt(s_NN)=200 GeV. The p_T of the photon is an excellent approximation to the initial p_T of the jet and the ratio z_T=p_T^h/p_T^γis used as a proxy for the jet fragmentation function. A statistical subtraction is used to extract the direct photon-hadron yields in Au+Au collisions while a photon isolation cut is applied in p+p. I_ AA, the ratio of jet fragment yield in Au+Au to that in p+p, indicates modification of the jet fragmentation function. Suppression, most likely due to energy loss in the medium, is seen at high z_T. The fragment yield at low z_T is enhanced at large angles. Such a trend is expected from redistribution of the lost energy into increased production of low-momentum particles.

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arXiv2012

J/psi suppression at forward rapidity in Au+Au collisions at sqrt(s_NN)=39 and 62.4 GeV

We present measurements of the J/psi invariant yields in sqrt(s_NN)=39 and 62.4 GeV Au+Au collisions at forward rapidity (1.2<|y|<2.2). Invariant yields are presented as a function of both collision centrality and transverse momentum. Nuclear modifications are obtained for central relative to peripheral Au+Au collisions (R_CP) and for various centrality selections in Au+Au relative to scaled p+p cross sections obtained from other measurements (R_AA). The observed suppression patterns at 39 and 62.4 GeV are quite similar to those previously measured at 200 GeV. This similar suppression presents a challenge to theoretical models that contain various competing mechanisms with different energy dependencies, some of which cause suppression and others enhancement.

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arXiv2012

sPHENIX: An Upgrade Concept from the PHENIX Collaboration

The PHENIX collaboration presents a concept for a major upgrade to the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC). This upgrade, referred to as sPHENIX, brings exciting new capability to the RHIC program by opening new and important channels for experimental investigation and utilizing fully the luminosity of the recently upgraded RHIC facility. sPHENIX enables a compelling jet physics program that will address fundamental questions about the nature of the strongly coupled quark-gluon plasma discovered experimentally at RHIC to be a perfect fluid. The upgrade concept addresses specific questions whose answers are necessary to advance our understanding of the quark-gluon plasma: (1) How to reconcile the observed strongly coupled quark-gluon plasma with the asymptotically free theory of quarks and gluons? (2) What are the dynamical changes to the quark-gluon plasma in terms of quasiparticles and excitations as a function of temperature? (3) How sharp is the transition of the quark-gluon plasma from the most strongly coupled regime near Tc to a weakly coupled system of partons known to emerge at asymptotically high temperatures? In three Appendices, we detail the additional physics capabilities gained through further upgrades: (A) two midrapidity detector additions, (B) a forward rapidity upgrade, and (C) an evolution to an ePHENIX detector suitable for a future Electron Ion Collider at RHIC.

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