arXiv subjects

M. Inaba

Publications and source records attributed to M. Inaba.

27 records · Page 2Linked to original sources

arXiv2019

Nonperturbative transverse momentum broadening in dihadron angular correlations in $\sqrt{s_{NN}}=200$ GeV proton-nucleus collisions

The PHENIX collaboration has measured high-$p_T$ dihadron correlations in $p$$+$$p$, $p$$+$Al, and $p$$+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV. The correlations arise from inter- and intra-jet correlations and thus have sensitivity to nonperturbative effects in both the initial and final states. The distributions of $p_{\rm out}$, the transverse momentum component of the associated hadron perpendicular to the trigger hadron, are sensitive to initial and final state transverse momenta. These distributions are measured multi-differentially as a function of $x_E$, the longitudinal momentum fraction of the associated hadron with respect to the trigger hadron. The near-side $p_{\rm out}$ widths, sensitive to fragmentation transverse momentum, show no significant broadening between $p$$+$Au, $p$$+$Al, and $p$$+$$p$. The away-side nonperturbative $p_{\rm out}$ widths are found to be broadened in $p$$+$Au when compared to $p$$+$$p$; however, there is no significant broadening in $p$$+$Al compared to $p$$+$$p$ collisions. The data also suggest that the away-side $p_{\rm out}$ broadening is a function of $N_{\rm coll}$, the number of binary nucleon-nucleon collisions, in the interaction. The potential implications of these results with regard to initial and final state transverse momentum broadening and energy loss of partons in a nucleus, among other nuclear effects, are discussed.

hep-ex↗

arXiv2019

Measurements of $μμ$ pairs from open heavy flavor and Drell-Yan in $p+p$ collisions at $\sqrt{s}=200$ GeV

PHENIX reports differential cross sections of $μμ$ pairs from semileptonic heavy-flavor decays and the Drell-Yan production mechanism measured in $p$$+$$p$ collisions at $\sqrt{s}=200$ GeV at forward and backward rapidity ($1.2<|η|<2.2$). The $μμ$ pairs from $c\bar{c}$, $b\bar{b}$, and Drell-Yan are separated using a template fit to unlike- and like-sign muon pair spectra in mass and $p_T$. The azimuthal opening angle correlation between the muons from $c\bar{c}$ and $b\bar{b}$ decays and the pair-$p_T$ distributions are compared to distributions generated using {\sc pythia} and {\sc powheg} models, which both include next-to-leading order processes. The measured distributions for pairs from $c\bar{c}$ are consistent with {\sc pythia} calculations. The $c\bar{c}$ data presents narrower azimuthal correlations and softer $p_T$ distributions compared to distributions generated from {\sc powheg}. The $b\bar{b}$ data are well described by both models. The extrapolated total cross section for bottom production is $3.75{\pm}0.24({\rm stat}){\pm}^{0.35}_{0.50}({\rm syst}){\pm}0.45({\rm global})$[$μ$b], which is consistent with previous measurements at the Relativistic Heavy Ion Collider in the same system at the same collision energy, and is approximately a factor of two higher than the central value calculated with theoretical models. The measured Drell-Yan cross section is in good agreement with next-to-leading-order quantum-chromodynamics calculations.

hep-ex↗

arXiv2018

Nonperturbative transverse-momentum-dependent effects in dihadron and direct photon-hadron angular correlations in $p+p$ collisions at $\sqrt{s}=200$ GeV

Dihadron and isolated direct photon-hadron angular correlations are measured in $p$$+$$p$ collisions at $\sqrt{s}=200$ GeV. The correlations are sensitive to nonperturbative initial-state and final-state transverse momentum $k_T$ and $j_T$ in the azimuthal nearly back-to-back region $Δϕ\simπ$. In this region, transverse-momentum-dependent evolution can be studied when several different hard scales are measured. To have sensitivity to small transverse momentum scales, nonperturbative momentum widths of $p_{\rm out}$, the out-of-plane transverse momentum component perpendicular to the trigger particle, are measured. These widths are used to investigate possible effects from transverse-momentum-dependent factorization breaking. When accounting for the longitudinal momentum fraction of the away-side hadron with respect to the near-side trigger particle, the widths are found to increase with the hard scale; this is qualitatively similar to the observed behavior in Drell-Yan and semi-inclusive deep-inelastic scattering interactions. The momentum widths are also studied as a function of center-of-mass energy by comparing to previous measurements at $\sqrt{s}=510$ GeV. The nonperturbative jet widths also appear to increase with $\sqrt{s}$ at a similar $x_T$, which is qualitatively consistent to similar measurements in Drell-Yan interactions. To quantify the magnitude of any transverse-momentum-dependent factorization breaking effects, calculations will need to be performed to compare to these measurements.

hep-ex↗

arXiv2018

Single-spin asymmetry of $J/ψ$ production in $p$$+$$p$, $p$$+$Al, and $p$$+$Au collisions with transversely polarized proton beams at $\sqrt{s_{_{NN}}}=200$ GeV

We report the transverse single-spin asymmetries of $J/ψ$ production at forward and backward rapidity, $1.2<|y|<2.2$, as a function of $J/ψ$ transverse momentum ($p_T$) and Feynman-$x$ ($x_F$). The data analyzed were recorded by the PHENIX experiment at the Relativistic Heavy Ion Collider in 2015 from $p$$+$$p$, $p$$+$Al, and $p$$+$Au collisions with transversely polarized proton beams at $\sqrt{s_{_{NN}}}=200$ GeV. At this collision energy, single-spin asymmetries for heavy-flavor particle production of $p$$+$$p$ collisions provide access to the spin-dependent gluon distribution and higher-twist correlation functions inside the nucleon, such as the gluon Qiu-Sterman and trigluon correlation functions. Proton+nucleus collisions offer an excellent opportunity to study nuclear effects on the correlation functions. The data indicate negative asymmetries at the two-standard-deviation level in the $p$$+$Au data for $p_T<2$ GeV/$c$ at both forward and backward rapidity, while in $p$$+$$p$ and $p$$+$Al collisions the asymmetries are consistent with zero within the range of experimental uncertainties.

hep-ex↗

arXiv2018

Correlations of $μμ$, $eμ$, and $ee$ pairs in $p$+$p$ collisions at $\sqrt{s}=200$ GeV and implications for $c\bar{c}$ and $b\bar{b}$ production mechanisms

PHENIX has measured the azimuthal correlations of muon pairs from charm and bottom semi-leptonic decays in $p$+$p$ collisions at $\sqrt{s}=200$ GeV, using a novel analysis technique utilizing both unlike- and like-sign muon pairs to separate charm, bottom and Drell-Yan contributions. The dimuon measurements combined with the previous electron-muon and dielectron measurements span a wide range in rapidity, and are well described by PYTHIA Tune A. Through a Bayesian analysis based on PYTHIA Tune A, we show that leading order pair creation is the dominant $(76\%\pm^{14}_{19}\%)$ contribution for $b\bar{b}$ production, whereas the data favor the scenario in which next-to-leading-order processes dominate $c\bar{c}$ production. The small contribution of next-to-leading-order processes in $b\bar{b}$ production at the collision energies of the Relativistic Heavy Ion Collider contrasts with the case at Large-Hadron-Collider energies, where next-to-leading-order processes are expected to dominate.

hep-ex↗

arXiv2017

Measurements of azimuthal anisotropy and charged-particle multiplicity in $d$$+$Au collisions at $\sqrt{s_{_{NN}}}=$200, 62.4, 39, and 19.6 GeV

We present measurements of the elliptic flow, $v_2$, as a function of transverse momentum ($p_T$), pseudorapidity ($η$), and centrality in $d$$+$Au collisions at $\sqrt{s_{_{NN}}}=$200, 62.4, 39, and 19.6 GeV. The beam-energy scan of $d$$+$Au collisions provides a testing ground for the onset of flow signatures in small collision systems. We measure a nonzero $v_2$ signal at all four collision energies, which, at midrapidity and low $p_T$, is consistent with predictions from viscous hydrodynamic models. Comparisons with calculations from parton transport models (based on the {\sc ampt} Monte Carlo generator) show good agreement with the data at midrapidity to forward ($d$-going) rapidities and low $p_T$. At backward (Au-going) rapidities and $p_T>1.5$ GeV/$c$, the data diverges from {\sc ampt} calculations of $v_2$ relative to the initial geometry, indicating the possible dominance of nongeometry related correlations, referred to as nonflow. We also present measurements of the charged-particle multiplicity ($dN_{\rm ch}/dη$) as a function of $η$ in central $d$$+$Au collisions at the same energies. We find that in $d$$+$Au collisions at $\sqrt{s_{_{NN}}}=$200 GeV the $v_2$ scales with $dN_{\rm ch}/dη$ over all $η$ in the PHENIX acceptance. At $\sqrt{s_{_{NN}}}=$62.4, and 39 GeV, $v_2$ scales with $dN_{\rm ch}/dη$ at midrapidity and forward rapidity, but falls off at backward rapidity. This departure from the $dN_{\rm ch}/dη$ scaling may be a further indication of nonflow effects dominating at backward rapidity.

nucl-ex↗

arXiv2017

Measurement of long-range angular correlations and azimuthal anisotropies in high-multiplicity $p$$+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV

We present the first measurements of long-range angular correlations and the transverse momentum dependence of elliptic flow $v_2$ in high-multiplicity $p$$+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV. A comparison of these results with previous measurements in high-multiplicity $d$$+$Au and $^3{\rm He}$$+$Au collisions demonstrates a relation between $v_2$ and the initial collision eccentricity $\varepsilon_2$, suggesting that the observed momentum-space azimuthal anisotropies in these small systems have a collective origin and reflect the initial geometry. Good agreement is observed between the measured $v_2$ and hydrodynamic calculations for all systems, and an argument disfavoring theoretical explanations based on momentum-space domain correlations is presented. The set of measurements presented here allows us to leverage the distinct intrinsic geometry of each of these systems to distinguish between different theoretical descriptions of the long-range correlations observed in small collision systems.

nucl-ex↗

arXiv2011

A Reaction Plane Detector for PHENIX at RHIC

A plastic scintillator paddle detector with embedded fiber light guides and photomultiplier tube readout, referred to as the Reaction Plane Detector (RXNP), was designed and installed in the PHENIX experiment prior to the 2007 run of the Relativistic Heavy Ion Collider (RHIC). The RXNP's design is optimized to accurately measure the reaction plane (RP) angle of heavy-ion collisions, where, for mid-central $\sqrt{s_{NN}}$ = 200 GeV Au+Au collisions, it achieved a $2^{nd}$ harmonic RP resolution of $\sim$0.75, which is a factor of $\sim$2 greater than PHENIX's previous capabilities. This improvement was accomplished by locating the RXNP in the central region of the PHENIX experiment, where, due to its large coverage in pseudorapidity ($1.0<|η|<2.8$) and $ϕ$ (2$π$), it is exposed to the high particle multiplicities needed for an accurate RP measurement. To enhance the observed signal, a 2-cm Pb converter is located between the nominal collision region and the scintillator paddles, allowing neutral particles produced in the heavy-ion collisions to contribute to the signal through conversion electrons. This paper discusses the design, operation and performance of the RXNP during the 2007 RHIC run.

nucl-ex↗

arXiv1996

Néel and singlet RVB orders in the t-J model

The Néel and the singlet RVB orders of the {\it t-J} model in a 2D square lattice are studied in the slave-boson mean-field approximation. It is shown that the Néel order parameter takes the maximum value at the finite temperature and disappear at the lower temperature for a certain range of doping. It is also shown that the Néel and the singlet RVB orders coexist at low temperature. This suggests the possibility of the coexistence of the Néel and the superconducting orders.

cond-mat↗