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Gubler, P.; Bratkovskaya, E.*; Song, T.*
EPJ Web of Conferences, 274, p.07015_1 - 07015_6, 2022/12
There is presently no consensus on how the meson mass and width will change once it is put in a dense environment such as nuclear matter. While many theoretical works exist, connecting them with experimental measurements remains non-trivial task, as the
meson in nuclear matter is usually produced in relatively high-energy pA (p: proton, A: nucleus) reactions, which are generally non-equilibrium processes. In this presentation I will report on an ongoing project, attempting to simulate pA reactions in which the
meson is produced in nuclei, making use of a transport approach. Results of simulations of 12 GeV/30 GeV p+C and p+Cu reactions will be presented and comparisons between obtained dilepton spectra and experimental data of the E325 experiment at KEK will be made. Furthermore, predictions for the ongoing J-PARC E16 experiment for both dilepton and
spectra will be given and discussed.
Gubler, P.; Bratkovskaya, E.*
EPJ Web of Conferences, 271, p.09004_1 - 09004_4, 2022/11
There is presently no consensus on how the meson mass and width will change once it is put in a dense environment such as nuclear matter. While many theoretical works exist, connecting them with experimental measurements remains non-trivial task, as the
meson in nuclear matter is usually produced in high-energy pA reactions, which are generally non-equilibrium processes. In this presentation I will report on an ongoing project, attempting to simulate pA reactions in which the
meson is produced in nuclei, making use of a transport approach. Results of simulations of 12 GeV/30 GeV p+C and p+Cu reactions will be presented and comparisons between obtained dilepton spectra and experimental data of the E325 experiment at KEK will be made. Furthermore, predictions for the ongoing J-PARC E16 experiment for both dilepton and
spectra will be given and discussed.
Gubler, P.; 山本 直希*; Yang, D.-L.*
Journal of Cosmology and Astroparticle Physics (Internet), 2022(9), p.025_1 - 025_36, 2022/09
被引用回数:0 パーセンタイル:0.01(Astronomy & Astrophysics)We investigate polarized gravitational waves generated by chiral fermions in the early Universe. In particular, we focus on the contribution from left-handed neutrinos in thermal equilibrium with finite temperature and chemical potential in the radiation dominated era. We compute the correlation functions of gravitational fields pertinent to the Stokes parameter V characterizing the circular polarization of gravitational waves in the Minkowski and expanding spacetime backgrounds. In the expanding universe, we find that the thermalized neutrinos induce a non-vanishing V linear to the neutrino degeneracy parameter and wavenumber of gravitational waves in the long wavelength region. While the magnitude of the gravitational waves generated by thermal neutrinos is too small to be detectable by current and planned third generation gravitational wave detectors, their observations by future generation detectors for ultra-high frequency regimes could provide information on the neutrino degeneracy parameter in the early Universe.
長村 尚弘*; Gubler, P.; 山中 長閑*
Journal of High Energy Physics (Internet), 2022(6), p.072_1 - 072_30, 2022/06
被引用回数:2 パーセンタイル:75.62(Physics, Particles & Fields)The contribution of the CP violating three-gluon Weinberg operator to the atomic and nuclear EDMs is estimated using QCD sum rules. After calculating the transition matrix element between the pion and the vacuum through the Weinberg operator, we obtain the long-range CP-odd nuclear force by determining the isovector CP-odd pion-nucleon vertex, using chiral perturbation theory at NLO. The EDMs of Hg,
Xe, and
Ra atoms, as well as those of
H and
He nuclei are finally given including comprehensive uncertainty analysis. While the leading contribution of the
Hg EDM is given by the intrinsic nucleon EDM, that of
Xe atom may be dominated by the one-pion exchange CP-odd nuclear force generated by the Weinberg operator. From current experimental data of the
Hg atomic EDM, we obtain an upper limit on the Weinberg operator magnitude of
if we assume that it is the only source of CP violation at the scale
= 1 TeV.
Kim, J.*; Gubler, P.; Lee, S. H.*
Physical Review D, 105(11), p.114053_1 - 114053_9, 2022/06
被引用回数:0 パーセンタイル:0.01(Astronomy & Astrophysics)The modification of the meson spectrum in nuclear matter is studied in an updated QCD sum rule analysis, taking into account recent improvements in properly treating the chiral invariant and breaking components of four-quark condensates. Allowing both mass and decay width to change at finite density, the QCD sum rule analysis determines certain combinations of changes for these parameters that satisfy the sum rules equally well. A comprehensive error analysis, including uncertainties related to the behavior of various condensates at linear order in density, the employed renormalization scale and perturbative corrections of the Wilson coefficients, is used to compute the allowed ranges of these parameter combinations. We find that the
meson mass shift in nuclear matter is especially sensitive to the strange sigma term
, which determines the decrease of the strange quark condensate in nuclear matter.
Gubler, P.
Proceedings of Science (Internet), 380, p.215_1 - 215_5, 2022/05
最近の研究成果に基づき、有限密度におけるメソンを実験的に調べるためのpA(p:陽子, A:原子核)反応の数値シミュレーションについて解説する。特に、
メソンのスペクトル関数の核物質中における変形が実験的に観測されるdi-leptonのスペクトルにいかに反映されるかについて詳しく議論する。
Gubler, P.
Few-Body Systems, 62(3), p.53_1 - 53_5, 2021/09
被引用回数:0 パーセンタイル:0(Physics, Multidisciplinary)最近の研究成果に基づき、有限密度におけるメソンを実験的に調べるためのpA(p:陽子, A:原子核)反応の数値シミュレーションについて解説する。特に、
メソンのスペクトル関数の核物質中における変形が実験的に観測されるdi-leptonのスペクトルにいかに反映されるかについて詳しく議論する。
Pavao, R.*; Gubler, P.; Fernandez-Soler, P.*; Nieves, J.*; 岡 眞; 高橋 徹*
Physics Letters B, 820, p.136473_1 - 136473_8, 2021/09
被引用回数:3 パーセンタイル:67.04(Astronomy & Astrophysics)The spectrum of the negative-parity spin-1/2 baryons is studied using lattice QCD and hadronic effective theory in a unitarized coupled-channel framework. A direct comparison between the two approaches is possible by considering the hadronic effective theory in a finite volume and with hadron masses and mesonic decay constants that correspond to the situation studied on the lattice. Comparing the energy level spectrum and
flavor decompositions of the individual states, itis found that the lowest two states extracted from lattice QCD can be identified with one of the two
(1405)-poles and the
(1670) resonance. The quark mass dependences of these two lattice QCD levels are in good agreement with their effective theory counterparts.
Meng, Q.*; 肥山 詠美子*; 保坂 淳; 岡 眞; Gubler, P.; Can, K. U.*; 高橋 徹*; Zong, H. S.*
Physics Letters B, 814, p.136095_1 - 136095_6, 2021/03
被引用回数:22 パーセンタイル:98.85(Astronomy & Astrophysics)Bound states of double-heavy tetraquarks are studied in a constituent quark model. Two bound states are found for isospin and spin-parity in the
channel. One is deeply bound and compact made of colored diquarks, while the other is shallow and extended as a
molecule. The former agrees well with lattice QCD results. A systematic decrease in the binding energy is seen by replacing one of the heavy quarks to a lighter one. Altogether we find ten bound states. It is shown for the first time that hadrons with totally different natures emerge from a single Hamiltonian.
Song, T.*; Gubler, P.; Hong, J.*; Lee, S. H.*; 森田 健司*
Physics Letters B, 813, p.136065_1 - 136065_5, 2021/02
被引用回数:1 パーセンタイル:32.08(Astronomy & Astrophysics)We calculate the mass shift and thermal decay width of the J/ near the QCD transition temperature
by imposing two independent constraints on these variables that can be obtained first by solving the Schrodinger equation and second from the QCD sum rule approach. While the real part of the potential is determined by comparing the QCD sum rule result for charmonium and the D meson to that from the potential model result, the imaginary potential is taken to be proportional to the perturbative form multiplied by a constant factor, which in turn can be determined by applying the two independent constraints. The result shows that the binding energy and the thermal width becomes similar in magnitude at around T = 1.09
, above which the sum rule analysis also becomes unstable, strongly suggesting that the J/
will melt slightly above
.
Gubler, P.
Journal of Physics; Conference Series, 1643, p.012009_1 - 012009_6, 2020/12
被引用回数:0 パーセンタイル:0.09研究成果に基づき、メソンの有限密度における振る舞いについて議論する。特に有限運動量の影響については最近の研究に進展があったため、詳しく議論する。また、時間が許せば、有限密度における
メソンを実験的に調べるためのpA(p: 陽子、A: 原子核)反応の最近行っている数値シミュレーションについても説明する。
Bahtiyar, H.*; Can, K. U.*; Erkol, G.*; Gubler, P.; 岡 眞; 高橋 徹*
Physical Review D, 102(5), p.054513_1 - 054513_18, 2020/09
被引用回数:19 パーセンタイル:86.72(Astronomy & Astrophysics)格子QCDによる第一原理計算を用いて、正負パリティのチャームバリオンの基底および励起状態のスペクトルを求めた。チャームクォークを1個, 2個あるいは3個含むバリオンの正および負パリティ状態の質量を、第一原理計算から求めることで、これまでの実験データや模型計算結果との比較を行い、その物理的な意味を解析することが可能となる。今回の計算では、パイオンの質量が観測値に十分近い物理点に近い領域で、2+1フレーバーのゲージ配位を用いた解析を行った。ディラック行列などの配置の異なる複数の演算子を用意し、その交差相関関数を計算し、固有値を求める方法により、基底状態と励起状態のスペクトルを計算した。
Gubler, P.
Hadron Spectroscopy and Structure; Proceedings of the 18th International Conference (HADRON 2019), p.694 - 698, 2020/08
最近の研究成果に基づき、有限密度におけるメソンを実験的に調べるためのpA(p:陽子、A:原子核)反応の数値シミュレーションについて解説する。特に、
メソンのスペクトル関数の核物質中における変形が実験的に観測されるdi-leptonのスペクトルにいかに反映されるかについて詳しく議論する。
田屋 英俊*; Park, A.*; Cho, S.*; Gubler, P.; 服部 恒一*; Hong, J.*; Huang, X.-G.*; Lee, S. H.*; 門内 明彦*; 大西 明*; et al.
Physical Review C, 102(2), p.021901_1 - 021901_6, 2020/08
被引用回数:6 パーセンタイル:71.34(Physics, Nuclear)We investigate the hadron production from the vortical quark-gluon plasma created in heavy-ion collisions. Based on the quark-coalescence and statistical hadronization models, we show that total hadron yields summed over the spin components are enhanced by the local vorticity with quadratic dependence. The enhancement factor amounts to be a few percent and may be detectable within current experimental sensitivities. We also show that the effect is stronger for hadrons with larger spin, and thus propose a new signature of the local vorticity, which may be detected by the yield ratio of distinct hadron species having different spins such as and
. The vorticity dependence of hadron yields seems robust, with consistent predictions in both of the hadron production mechanisms for reasonable values of the vorticity strength estimated for heavy-ion collisions.
Gubler, P.
AIP Conference Proceedings 2249, p.030002_1 - 030002_7, 2020/07
被引用回数:0 パーセンタイル:0.09最近の研究成果に基づき、メソンを原子核中に生成するためのpA反応(p:陽子、A:原子核)の数値的シミュレーションに関する発表を行う。特に、実験的に観測されるdi-lepton spectrumの形を詳細に説明し、
メソンはどのようなスペクトル関数を持っていれば、実験結果を再現できるかについて議論する。
Gubler, P.; Song, T.*; Lee, S. H.*
Physical Review D, 101(11), p.114029_1 - 114029_10, 2020/06
被引用回数:3 パーセンタイル:31.53(Astronomy & Astrophysics)Based on the observation that the heavy quark-antiquark potential value at infinity corresponds to twice the meson mass, we constrain the asymptotic value of the heavy quark potential in a hot medium through a QCD sum rule calculation of the
meson at finite temperature. We find that to correctly reproduce the QCD sum rule results as well as a recent model calculation for the
meson mass near the critical temperature, the heavy quark potential should be composed mostly of the free energy with an addition of a small but non-trivial fraction of the internal energy. Combined with a previous study comparing potential model results for the J/
to a QCD sum rule calculation, we conclude that the composition of the effective heavy quark potential should depend on the inter-quark distance. Namely, the potential is dominated by the free energy at short distance, while at larger separation, it has a fraction of about 20% of internal energy.
Kim, H.-J.*; Gubler, P.
Physics Letters B, 805, p.135412_1 - 135412_8, 2020/06
被引用回数:5 パーセンタイル:65.07(Astronomy & Astrophysics)QCD和則を利用し、核物質におけるメソンの分散関係を調べる。敗れたLorentz対称性により、有限密度中ではベクター粒子のlongitudinal及びtransverseモードが異なる振る舞いを示しえる。次元6までの可能な演算子及びそのWilson係数をすべて用い、様々な密度及び運動量における
メソンの分散関係を解析する。その結果、longitudinal及びtransverseモードが逆の振る舞いを示すことが分かった。実際、運動量1GeVでは、longitudinalモードでは質量が5MeVほど下り、transverseモードでは7MeVほど上がることが分かった。longitudinal及びtransverseモードを区別しない実験では、この現象が二つの分離されたピークとして観測される可能性がある。
Gubler, P.; 佐藤 大輔*
JPS Conference Proceedings (Internet), 26, p.024023_1 - 024023_5, 2019/11
本講演では最近の発表論文に基づき、vectorチャンネル(光子と同じ量子数を持つ状態)のスペクトル関数に関して導出したいくつかの厳密な和則を紹介する。摂動計算ではこの和則が成り立つことや、格子QCDへの応用についても議論する。
Can, K. U.*; Bahtiyar, H.*; Erkol, G.*; Gubler, P.; 岡 眞; 高橋 徹*
JPS Conference Proceedings (Internet), 26, p.022028_1 - 022028_5, 2019/11
格子QCDによる第一原理計算を用いて、チャームバリオンの基底および励起状態のスペクトルを求めた。
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
被引用回数:0Several 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.