Meng, Q.*; 肥山 詠美子*; Can, K. U.*; Gubler, P.; 岡 眞; 保坂 淳; Zong, H.*
Physics Letters B, 798, p.135028_1 - 135028_8, 2019/11
Several compact pentaquark resonances are predicted in a potential quark model. The Hamiltonian is the best available one, which reproduces the masses of the low-lying charmed and strange hadrons well. Full five-body calculations are carried out by the use of the Gaussian expansion method, and the relevant baryon-meson thresholds are taken into account explicitly. Employing the real scaling method, we predict four sharp resonances, ( = 5180 MeV, = 20 MeV) and others. These are the candidates of compact pentaquark resonance states from the current best quark model, which should be confirmed either by experiments or lattice QCD calculations.
岩崎 幸生; 岡 眞; 鈴木 渓*; 吉田 哲也*
International Journal of Modern Physics; Conference Series (Internet), 49, p.1960002_1 - 1960002_6, 2019/07
Kim, H.*; Kim, K. S.*; Cheoun, M.-K.*; 慈道 大介*; 岡 眞
Physical Review D, 99(1), p.014005_1 - 014005_15, 2019/01
肥山 詠美子; 保坂 淳; 岡 眞; Richard, J.-M.*
Physical Review C, 98(4), p.045208_1 - 045208_8, 2018/10
Kim, H.*; Kim, K. S.*; Cheoun, M.-K.*; 岡 眞
Physical Review D, 97(9), p.094005_1 - 094005_17, 2018/05
Adare, A.*; 長谷川 勝一; 今井 憲一; 永宮 正治; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他497名*
Physical Review C, 96(2), p.024907_1 - 024907_19, 2017/08
We report a measurement of pairs from semileptonic heavy-flavor decays in collisions at = 200 GeV. The pair yield from and is separated by exploiting a double differential fit done simultaneously in dielectron invariant mass and . We used three different event generators, , , and , to simulate the spectra from and production. The data can be well described by all three generators within the detector acceptance. However, when using the generators to extrapolate to , significant differences are observed for the total cross section. These difference are less pronounced for than for . The same model dependence was observed in already published data. The data are also directly compared with data in mass and , and within the statistical accuracy no nuclear modification is seen.
Adare, A.*; 長谷川 勝一; 今井 憲一; 永宮 正治; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他462名*
Physical Review D, 95(7), p.072002_1 - 072002_19, 2017/04
Dihadron and isolated direct photon-hadron angular correlations are measured in collisions at = 510 GeV. Correlations of charged hadrons of GeV/ with mesons of GeV/ or isolated direct photons of GeV/ are used to study nonperturbative effects generated by initial-state partonic transverse momentum and final-state transverse momentum from fragmentation. The nonperturbative behavior is characterized by measuring the out-of-plane transverse momentum component perpendicular to the axis of the trigger particle, which is the high- direct photon or . Nonperturbative evolution effects are extracted from Gaussian fits to the away-side inclusive-charged-hadron yields for different trigger-particle transverse momenta (). The Gaussian widths and root mean square of are reported as a function of the interaction hard scale to investigate possible transverse-momentum-dependent evolution differences between the - and direct photon- correlations and factorization breaking effects. The widths are found to decrease with , which indicates that the Collins-Soper-Sterman soft factor is not driving the evolution with the hard scale in nearly back-to-back dihadron and direct photon-hadron production in collisions. This behavior is in contrast to Drell-Yan and semi-inclusive deep-inelastic scattering measurements.
Adare, A.*; 長谷川 勝一; 今井 憲一; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他361名*
Physical Review C, 95(3), p.034904_1 - 034904_10, 2017/03
The PHENIX Collaboration has measured the ratio of the yields of to mesons produced in , Al, Au, and He+Au collisions at GeV over the forward and backward rapidity intervals . We find that the ratio in collisions is consistent with measurements at other collision energies. In collisions with nuclei, we find that in the forward (-going or He-going) direction, the relative yield of mesons to mesons is consistent with the value measured in collisions. However, in the backward (nucleus-going) direction, the meson is preferentially suppressed by a factor of . This suppression is attributed in some models to the breakup of the weakly bound meson through final-state interactions with comoving particles, which have a higher density in the nucleus-going direction. These breakup effects may compete with color screening in a deconfined quark-gluon plasma to produce sequential suppression of excited quarkonia states.
Aidala, C.*; 長谷川 勝一; 今井 憲一; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他304名*
Physical Review C, 95(3), p.034910_1 - 034910_10, 2017/03
We present measurements of long-range angular correlations and the transverse momentum dependence of elliptic flow in high-multiplicity + Au collisions at GeV. A comparison of these results to previous measurements in high-multiplicity + Au and He + Au collisions demonstrates a relation between and the initial collision eccentricity , 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 and hydrodynamic calculations for all systems, and an argument disfavoring theoretical explanations based on initial 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.
Adare, A.*; 長谷川 勝一; 今井 憲一; 永宮 正治; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他545名*
Physical Review C, 94(6), p.064901_1 - 064901_14, 2016/12
The PHENIX experiment at the BNL Relativistic Heavy Ion Collider has measured second- and third-order Fourier coefficients of the azimuthal distributions of direct photons emitted at midrapidity in Au+Au collisions at = 200 GeV for various collision centralities. Combining two different analysis techniques, results were obtained in the transverse momentum range of GeV/. At low the second-order coefficients, , are similar to the ones observed in hadrons. Third-order coefficients, , are nonzero and almost independent of centrality. These new results on and , combined with previously published results on yields, are compared to model calculations that provide yields and asymmetries in the same framework. Those models are challenged to explain simultaneously the observed large yield and large azimuthal anisotropies.
Adare, A.*; 長谷川 勝一; 今井 憲一; 永宮 正治; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他397名*
Physical Review C, 94(5), p.054910_1 - 054910_18, 2016/11
Measurements of anisotropic flow Fourier coefficients () for inclusive charged particles and identified hadrons , , , and produced at midrapidity in Cu+Au collisions at = 200 GeV are presented. The data were collected in 2012 by the PHENIX experiment at the Relativistic Heavy-Ion Collider (RHIC). The particle azimuthal distributions with respect to different-order symmetry planes , for 1, 2, and 3 are studied as a function of transverse momentum over a broad range of collision centralities. Mass ordering, as expected from hydrodynamic flow, is observed for all three harmonics. The charged-particle results are compared with hydrodynamical and transport model calculations. We also compare these Cu+Au results with those in Cu+Cu and Au+Au collisions at the same and find that the and , as a function of transverse momentum, follow a common scaling with .
Adare, A.*; 今井 憲一; 永宮 正治; 谷田 聖; PHENIX Collaboration*; 他385名*
Physical Review C, 93(5), p.051902_1 - 051902_8, 2016/05
Measurements of the anisotropic flow coefficients , , , and , for identified particles (, , and ) at midrapidity, obtained relative to the event planes at forward rapidities in Au + Au collisions at 200 GeV, are presented as a function of collision centrality and particle transverse momenta . The coefficients show characteristic patterns consistent with hydrodynamical expansion of the matter produced in the collisions. For each harmonic , a modified valence quark-number scaling [plotting versus transverse kinetic energies ] is observed to yield a single curve for all the measured particle species for a broad range of . A simultaneous blast-wave model fit to the observed coefficients and published particle spectra identifies radial flow anisotropies and spatial eccentricities at freeze-out. These are generally smaller than the initial-state participant-plane geometric eccentricities as also observed in the final eccentricity from quantum interferometry measurements with respect to the event plane.
Adare, A.*; 長谷川 勝一; 今井 憲一; 永宮 正治; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他397名*
Physical Review C, 93(3), p.034903_1 - 034903_12, 2016/03
The invariant yields, , for production at forward rapidity () in U+U collisions at = 193 GeV have been measured as a function of collision centrality. The invariant yields and nuclear-modification factor are presented and compared with those from Au + Au collisions in the same rapidity range. Additionally, the direct ratio of the invariant yields from U + U and Au + Au collisions within the same centrality class is presented, and used to investigate the role of coalescence. Two different parametrizations of the deformed Woods-Saxon distribution were used in Glauber calculations to determine the values of the number of nucleon-nucleon collisions in each centrality class, , and these were found to give significantly different values. Results using values from both deformed Woods-Saxon distributions are presented. The measured ratios show that the suppression, relative to binary collision scaling, is similar in U + U and Au + Au for peripheral and midcentral collisions, but that show less suppression for the most central U + U collisions. The results are consistent with a picture in which, for central collisions, increase in the yield due to coalescence becomes more important than the decrease in yield due to increased energy density. For midcentral collisions, the conclusions about the balance between coalescence and suppression depend on which deformed Woods-Saxon distribution is used to determine .
Adare, A.*; 長谷川 勝一; 今井 憲一; 永宮 正治; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他426名*
Physical Review C, 93(3), p.034904_1 - 034904_29, 2016/03
The PHENIX Collaboration at the Relativistic Heavy Ion Collider has measured open heavy flavor production in minimum bias Au + Au collisions at = 200 GeV via the yields of electrons from semileptonic decays of charm and bottom hadrons. Previous heavy flavor electron measurements indicated substantial modification in the momentum distribution of the parent heavy quarks owing to the quark-gluon plasma created in these collisions. For the first time, using the PHENIX silicon vertex detector to measure precision displaced tracking, the relative contributions from charm and bottom hadrons to these electrons as a function of transverse momentum are measured in Au + Au collisions. We compare the fraction of electrons from bottom hadrons to previously published results extracted from electron-hadron correlations in collisions at = 200 GeV and find the fractions to be similar within the large uncertainties on both measurements for 4 GeV/. We use the bottom electron fractions in Au + Au and along with the previously measured heavy flavor electron to calculate the for electrons from charm and bottom hadron decays separately. We find that electrons from bottom hadron decays are less suppressed than those from charm for the region 3 4 GeV/.
Adare, A.*; 今井 憲一; 長谷川 勝一; 永宮 正治; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他477名*
Physical Review Letters, 116(12), p.122301_1 - 122301_9, 2016/03
Jet production rates are measured in and Au collisions at = 200 GeV recorded in 2008 with the PHENIX detector at the Relativistic Heavy Ion Collider. Jets are reconstructed using the =0.3 anti- algorithm from energy deposits in the electromagnetic calorimeter and charged tracks in multiwire proportional chambers, and the jet transverse momentum () spectra are corrected for the detector response. Spectra are reported for jets with GeV/ within a pseudorapidity acceptance of . The nuclear-modification factor () values and central-to-peripheral ratios () show large, -dependent deviations from unity, challenging the conventional models that relate hard-process rates and soft-particle production in collisions involving nuclei.
Adare, A.*; 長谷川 勝一; 今井 憲一; 永宮 正治; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他623名*
Physical Review C, 93(2), p.024911_1 - 024911_20, 2016/02
Measurements of the fractional momentum loss () of high-transverse-momentum-identified hadrons in heavy-ion collisions are presented. Using in Au+Au and Cu+Cu collisions at = 62.4 and 200 GeV measured by the PHENIX experiment at the Relativistic Heavy Ion Collider and and charged hadrons in Pb+Pb collisions measured by the ALICE experiment at the Large Hadron Collider, we studied the scaling properties of as a function of a number of variables: the number of participants, , the number of quark participants, , the charged-particle density, , and the Bjorken energy density times the equilibration time, . We find that the , where has its maximum, varies both with centrality and collision energy. Above the maximum, tends to follow a power-law function with all four scaling variables. The data at = 200 and 2.76 TeV, for sufficiently high particle densities, have a common scaling of with and , lending insight into the physics of parton energy loss.
Adare, A.*; 今井 憲一; 永宮 正治; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他506名*
Physical Review C, 93(1), p.011901_1 - 011901_8, 2016/01
We report the measurement of cumulants (, ) of the net-charge distributions measured within pseudorapidity () in Au + Au collisions at = 7.7-200 GeV with the PHENIX experiment at the Relativistic Heavy Ion Collider. The ratios of cumulants (e.g., , ) of the net-charge distributions, which can be related to volume independent susceptibility ratios, are studied as a function of centrality and energy. These quantities are important to understand the quantum-chromodynamics phase diagram and possible existence of a critical end point. The measured values are very well described by expectation from negative binomial distributions. We do not observe any nonmonotonic behavior in the ratios of the cumulants as a function of collision energy. The measured values of and can be directly compared to lattice quantum-chromodynamics calculations and thus allow extraction of both the chemical freeze-out temperature and the baryon chemical potential at each center-of-mass energy. The extracted baryon chemical potentials are in excellent agreement with a thermal-statistical analysis model.
Adare, A.*; 長谷川 勝一; 今井 憲一; 永宮 正治; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他477名*
Physical Review C, 92(4), p.044909_1 - 044909_14, 2015/10
The PHENIX Collaboration has measured meson production in + Au collisions at = 200 GeV using the dimuon and dielectron decay channels. The meson is measured in the forward (backward) -going (Au-going) direction, in the transverse-momentum () range from 1-7 GeV/ and at midrapidity in the range below 7 GeV/. The meson invariant yields and nuclear-modification factors as a function of , rapidity, and centrality are reported. An enhancement of meson production is observed in the Au-going direction, while suppression is seen in the -going direction, and no modification is observed at midrapidity relative to the yield in collisions scaled by the number of binary collisions. Similar behavior was previously observed for inclusive charged hadrons and open heavy flavor, indicating similar cold-nuclear-matter effects.