J. R. Adams

Bio: J. R. Adams is an academic researcher from Ohio State University. The author has contributed to research in topics: Pion & Order (ring theory). The author has an hindex of 15, co-authored 60 publications receiving 1422 citations.

Identified Particle Distributions inppandAu+AuCollisions atsNN=200GeV

Abstract: Transverse mass and rapidity distributions for charged pions, charged kaons, protons, and antiprotons are reported for $\sqrt{{s}_{NN}}=200\text{ }\text{ }\mathrm{GeV}$ $pp$ and $\mathrm{Au}+\mathrm{Au}$ collisions at Relativistic Heary Ion Collider (RHIC). Chemical and kinetic equilibrium model fits to our data reveal strong radial flow and long duration from chemical to kinetic freeze-out in central $\mathrm{Au}+\mathrm{Au}$ collisions. The chemical freeze-out temperature appears to be independent of initial conditions at RHIC energies.

Strange particle production inp+pcollisions ats=200GeV

Abstract: We present strange particle spectra and yields measured at midrapidity in $\sqrt{s}=200$ GeV proton-proton ($p+p$) collisions at the BNL Relativistic Heavy Ion Collider (RHIC). We find that the previously observed universal transverse mass (${m}_{T}\ensuremath{\equiv}\sqrt{{{p}_{T}}^{2}+{m}^{2}}$) scaling of hadron production in $p+p$ collisions seems to break down at higher ${m}_{T}$ and that there is a difference in the shape of the ${m}_{T}$ spectrum between baryons and mesons. We observe midrapidity antibaryon to baryon ratios near unity for \ensuremath{\Lambda} and \ensuremath{\Xi} baryons and no dependence of the ratio on transverse momentum, indicating that our data do not yet reach the quark-jet dominated region. We show the dependence of the mean transverse momentum $\ensuremath{\langle}{p}_{T}\ensuremath{\rangle}$ on measured charged particle multiplicity and on particle mass and infer that these trends are consistent with gluon-jet dominated particle production. The data are compared with previous measurements made at the CERN Super Proton Synchrotron and Intersecting Storage Rings and in Fermilab experiments and with leading-order and next-to-leading-order string fragmentation model predictions. We infer from these comparisons that the spectral shapes and particle yields from $p+p$ collisions at RHIC energies have large contributions from gluon jets rather than from quark jets.

Open Charm Yields in dAu Collisions at sNN p 200 GeV

Abstract: Mid-rapidity open charm spectra from direct reconstruction of D{sup 0}({bar D}{sup 0}) {yields} K{sup {-+}} {pi}{sup {+-}} in d+Au collisions and indirect electron/positron measurements via charm semileptonic decays in p+p and d+Au collisions at {radical}s{sub NN} = 200 GeV are reported. The D{sup 0}({bar D}{sup 0}) spectrum covers a transverse momentum (p{sub T}) range of 0.1 < p{sub T} < 3 GeV/c whereas the electron spectra cover a range of 1 < p{sub T} < 4 GeV/c. The electron spectra show approximate binary collision scaling between p+p and d+Au collisions. From these two independent analyses, the differential cross section per nucleon-nucleon binary interaction at mid-rapidity for open charm production from d+Au collisions at RHIC is d{sigma}{sub c{bar c}}{sup NN}/dy = 0.30 {+-} 0.04 (stat.) {+-} 0.09(syst.) mb. The results are compared to theoretical calculations. Implications for charmonium results in A+A collisions are discussed.

Forward Neutral Pion Production inp+pandd+AuCollisions atsNN=200GeV

Abstract: Measurements of the production of forward ${\ensuremath{\pi}}^{0}$ mesons from $p+p$ and $d+\mathrm{Au}$ collisions at $\sqrt{{s}_{NN}}=200\text{ }\text{ }\mathrm{GeV}$ are reported. The $p+p$ yield generally agrees with next-to-leading order perturbative QCD calculations. The $d+\mathrm{Au}$ yield per binary collision is suppressed as $\ensuremath{\eta}$ increases, decreasing to $\ensuremath{\sim}30%$ of the $p+p$ yield at $⟨\ensuremath{\eta}⟩=4.00$, well below shadowing expectations. Exploratory measurements of azimuthal correlations of the forward ${\ensuremath{\pi}}^{0}$ with charged hadrons at $\ensuremath{\eta}\ensuremath{\approx}0$ show a recoil peak in $p+p$ that is suppressed in $d+\mathrm{Au}$ at low pion energy. These observations are qualitatively consistent with a saturation picture of the low-$x$ gluon structure of heavy nuclei.

Nonmonotonic Energy Dependence of Net-Proton Number Fluctuations

Abstract: Nonmonotonic variation with collision energy (sqrt[s_{NN}]) of the moments of the net-baryon number distribution in heavy-ion collisions, related to the correlation length and the susceptibilities of the system, is suggested as a signature for the quantum chromodynamics critical point. We report the first evidence of a nonmonotonic variation in the kurtosis times variance of the net-proton number (proxy for net-baryon number) distribution as a function of sqrt[s_{NN}] with 3.1 σ significance for head-on (central) gold-on-gold (Au+Au) collisions measured solenoidal tracker at Relativistic Heavy Ion Collider. Data in noncentral Au+Au collisions and models of heavy-ion collisions without a critical point show a monotonic variation as a function of sqrt[s_{NN}].

Tuning Monte Carlo Generators: The Perugia Tunes

Abstract: We present 9 new tunes of the p{sub perpendicular}-ordered shower and underlying-event model in Pythia 6.4. These 'Perugia' tunes update and supersede the older 'S0' family. The data sets used to constrain the models include hadronic Z{sup 0} decays at LEP, Tevatron min-bias data at 630, 1800, and 1960 GeV, Tevatron Drell-Yan data at 1800 and 1960 GeV, and SPS min-bias data at 200, 546, and 900 GeV. In addition to the central parameter set, called 'Perugia 0', we introduce a set of 8 related 'Perugia variations' that attempt to systematically explore soft, hard, parton density, and color structure variations in the theoretical parameters. Based on these variations, a best-guess prediction of the charged track multiplicity in inelastic, nondiffractive minimum-bias events at the LHC is made. Note that these tunes can only be used with Pythia 6, not with Pythia 8.

Electron-Ion Collider: The next QCD frontier: Understanding the glue that binds us all

Abstract: This White Paper presents the science case of an Electron-Ion Collider (EIC), focused on the structure and interactions of gluon-dominated matter, with the intent to articulate it to the broader nuclear science community. It was commissioned by the managements of Brookhaven National Laboratory (BNL) and Thomas Jefferson National Accelerator Facility (JLab) with the objective of presenting a summary of scientific opportunities and goals of the EIC as a follow-up to the 2007 NSAC Long Range plan. This document is a culmination of a community-wide effort in nuclear science following a series of workshops on EIC physics over the past decades and, in particular, the focused ten-week program on “Gluons and quark sea at high energies” at the Institute for Nuclear Theory in Fall 2010. It contains a brief description of a few golden physics measurements along with accelerator and detector concepts required to achieve them. It has been benefited profoundly from inputs by the users’ communities of BNL and JLab. This White Paper offers the promise to propel the QCD science program in the US, established with the CEBAF accelerator at JLab and the RHIC collider at BNL, to the next QCD frontier.