arXiv - PHYS - Nuclear Experiment最新文献

{"title":"Observation of double J/$ψ$ meson production in pPb collisions at $sqrt{s_mathrm{NN}}$ = 8.16 TeV","authors":"CMS Collaboration","doi":"arxiv-2407.03223","DOIUrl":"https://doi.org/arxiv-2407.03223","url":null,"abstract":"The first observation of the concurrent production of two J/$psi$ mesons in\u0000proton-nucleus collisions is presented. The analysis is based on a proton-lead\u0000(pPb) data sample recorded at a nucleon-nucleon center-of-mass energy of 8.16\u0000TeV by the CMS experiment at the CERN LHC and corresponding to an integrated\u0000luminosity of 174.6 nb$^{-1}$. The two J/$psi$ mesons are reconstructed in\u0000their $mu^+mu^-$ decay channels with transverse momenta $p_mathrm{T}$ $gt$\u00006.5 GeV and rapidity $lvert y rvert$ $lt$ 2.4. Events where one of the\u0000J/$psi$ mesons is reconstructed in the dielectron channel are also considered\u0000in the search. The pPb $to$ J/$psi$J/$psi$+X process is observed with a\u0000significance of 5.3 standard deviations. The measured inclusive fiducial cross\u0000section, using the four-muon channel alone, is $sigma$(pPb$to$\u0000J/$psi$J/$psi$+X)= 22.0 $pm$ 8.9 (stat) $pm$ 1.5 (syst) nb. A fit of the\u0000data to the expected rapidity separation for pairs of J/$psi$ mesons produced\u0000in single (SPS) and double (DPS) parton scatterings yields\u0000$sigma^{mathrm{pPb}tomathrm{J}/psimathrm{J}/psi+mathrm{X}}_text{SPS}$\u0000= 16.5 $pm$ 10.8 (stat) $pm$ 0.1 (syst) nb and $sigma^{mathrm{pPb}to\u0000mathrm{J}/psimathrm{J}/psi+mathrm{X}}_text{DPS}$ = 5.4 $pm$ 6.2 (stat)\u0000$pm$ 0.4 (syst) nb, respectively. This latter result can be transformed into a\u0000lower bound on the effective DPS cross section, closely related to the squared\u0000average interparton transverse separation in the collision, of\u0000$sigma_text{eff}$ $gt$ 1.0 mb at 95% confidence level.","PeriodicalId":501206,"journal":{"name":"arXiv - PHYS - Nuclear Experiment","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141550212","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An Upper Limit on the Photoproduction Cross Section of the Spin-Exotic $π_1(1600)$","authors":"F. Afzal, C. S. Akondi, M. Albrecht, M. Amaryan, S. Arrigo, V. Arroyave, A. Asaturyan, A. Austregesilo, Z. Baldwin, F. Barbosa, J. Barlow, E. Barriga, R. Barsotti, D. Barton, V. Baturin, V. V. Berdnikov, T. Black, W. Boeglin, M. Boer, W. J. Briscoe, T. Britton, S. Cao, E. Chudakov, G. Chung, P. L. Cole, O. Cortes, V. Crede, M. M. Dalton, D. Darulis, A. Deur, S. Dobbs, A. Dolgolenko, M. Dugger, R. Dzhygadlo, D. Ebersole, M. Edo, H. Egiyan, T. Erbora, P. Eugenio, A. Fabrizi, C. Fanelli, S. Fang, J. Fitches, A. M. Foda, S. Furletov, L. Gan, H. Gao, A. Gardner, A. Gasparian, D. Glazier, C. Gleason, V. S. Goryachev, B. Grube, J. Guo, L. Guo, J. Hernandez, K. Hernandez, N. D. Hoffman, D. Hornidge, G. Hou, P. Hurck, A. Hurley, W. Imoehl, D. G. Ireland, M. M. Ito, I. Jaegle, N. S. Jarvis, T. Jeske, M. Jing, R. T. Jones, V. Kakoyan, G. Kalicy, V. Khachatryan, C. Kourkoumelis, A. LaDuke, I. Larin, D. Lawrence, D. I. Lersch, H. Li, B. Liu, K. Livingston, G. J. Lolos, L. Lorenti, V. Lyubovitskij, R. Ma, D. Mack, A. Mahmood, H. Marukyan, V. Matveev, M. McCaughan, M. McCracken, C. A. Meyer, R. Miskimen, R. E. Mitchell, K. Mizutani, V. Neelamana, L. Ng, E. Nissen, S. Orešić, A. I. Ostrovidov, Z. Papandreou, C. Paudel, R. Pedroni, L. Pentchev, K. J. Peters, E. Prather, S. Rakshit, J. Reinhold, A. Remington, B. G. Ritchie, J. Ritman, G. Rodriguez, D. Romanov, K. Saldana, C. Salgado, S. Schadmand, A. M. Schertz, K. Scheuer, A. Schick, A. Schmidt, R. A. Schumacher, J. Schwiening, N. Septian, P. Sharp, X. Shen, M. R. Shepherd, J. Sikes, A. Smith, E. S. Smith, D. I. Sober, A. Somov, S. Somov, J. R. Stevens, I. I. Strakovsky, B. Sumner, K. Suresh, V. V. Tarasov, S. Taylor, A. Teymurazyan, A. Thiel, T. Viducic, T. Whitlatch, N. Wickramaarachchi, Y. Wunderlich, B. Yu, J. Zarling, Z. Zhang, X. Zhou, B. Zihlmann","doi":"arxiv-2407.03316","DOIUrl":"https://doi.org/arxiv-2407.03316","url":null,"abstract":"The spin-exotic hybrid meson $pi_{1}(1600)$ is predicted to have a large\u0000decay rate to the $omegapipi$ final state. Using 76.6~pb$^{-1}$ of data\u0000collected with the GlueX detector, we measure the cross sections for the\u0000reactions $gamma p to omega pi^+ pi^- p$, $gamma p to omega pi^0 pi^0\u0000p$, and $gamma ptoomegapi^-pi^0Delta^{++}$ in the range $E_gamma =$ 8-10\u0000GeV. Using isospin conservation, we set the first upper limits on the\u0000photoproduction cross sections of the $pi^{0}_{1}(1600)$ and\u0000$pi^{-}_{1}(1600)$. We combine these limits with lattice calculations of decay\u0000widths and find that photoproduction of $eta'pi$ is the most sensitive\u0000two-body system to search for the $pi_1(1600)$.","PeriodicalId":501206,"journal":{"name":"arXiv - PHYS - Nuclear Experiment","volume":"49 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141550211","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Heavy Flavor and Quarkonia Results from the PHENIX Experiment","authors":"Krista Smith","doi":"arxiv-2407.02451","DOIUrl":"https://doi.org/arxiv-2407.02451","url":null,"abstract":"The PHENIX experiment at RHIC has a unique large rapidity coverage ($1.2 <\u0000|y| < 2.2$) for heavy flavor studies in heavy-ion collisions. This kinematic\u0000region has a smaller particle density and may undergo different nuclear effects\u0000before and after the hard process when compared to mid-rapidity production. The\u0000latest PHENIX runs contain a large data set which allows, for the first time,\u0000the study of heavy flavor and $J/psi$ flow at the large rapidity region in\u0000Au$+$Au collisions at $sqrt{s_{_{NN}}}=$200 GeV. This measurement has the\u0000potential to reveal a medium evolution distinct from that known at\u0000mid-rapidity.","PeriodicalId":501206,"journal":{"name":"arXiv - PHYS - Nuclear Experiment","volume":"43 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141521028","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Measurement of the inclusive isolated-photon production cross section in pp collisions at $sqrt{s}$ = 13 TeV","authors":"ALICE Collaboration","doi":"arxiv-2407.01165","DOIUrl":"https://doi.org/arxiv-2407.01165","url":null,"abstract":"The production cross section of inclusive isolated photons has been measured\u0000by the ALICE experiment at the CERN LHC in pp collisions at centre-of-momentum\u0000energy of $sqrt{s}=13$ TeV collected during the LHC Run 2 data-taking period.\u0000The measurement is performed by combining the measurements of the\u0000electromagnetic calorimeter EMCal and the central tracking detectors ITS and\u0000TPC, covering a pseudorapidity range of $|eta^{gamma}|<0.67$ and a transverse\u0000momentum range of $7<p_{rm T}^{gamma}<200$ GeV/$c$. The result extends to\u0000lower $p_{rm T}^{gamma}$ and $x_{rm T}^{gamma} = 2p_{rm\u0000T}^{gamma}/sqrt{s}$ ranges, the lowest $x_{rm T}^{gamma}$ of any isolated\u0000photon measurements to date, extending significantly those measured by the\u0000ATLAS and CMS experiments towards lower $p_{rm T}^{gamma}$ at the same\u0000collision energy with a small overlap between the measurements. The measurement\u0000is compared with next-to-leading order perturbative QCD calculations and the\u0000results from the ATLAS and CMS experiments as well as with measurements at\u0000other collision energies. The measurement and theory prediction are in\u0000agreement with each other within the experimental and theoretical\u0000uncertainties.","PeriodicalId":501206,"journal":{"name":"arXiv - PHYS - Nuclear Experiment","volume":"49 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141529735","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Final results of the measurement to search for rare decays of naturally occurring osmium isotopes with ultra-low background gamma-ray spectrometry","authors":"P. Belli, R. Bernabei, F. Cappella, V. Caracciolo, R. Cerulli, F. A. Danevich, V. Yu. Denisov, A. Incicchitti, D. V. Kasperovych, V. V. Kobychev, G. P. Kovtun, M. Laubenstein, D. V. Poda, O. G. Polischuk, A. P. Shcherban, D. A. Solopikhin, S. Tessalina, V. I. Tretyak","doi":"arxiv-2406.19062","DOIUrl":"https://doi.org/arxiv-2406.19062","url":null,"abstract":"A long-term measurement was conducted to search for $alpha$, double-$alpha$\u0000and double-$beta$ decays with $gamma$ quanta emission in naturally occurring\u0000osmium isotopes. This study took advantage of two ultra-low background HPGe\u0000detectors and one ultra-low background BEGe detector at the Gran Sasso National\u0000Laboratory (LNGS) of the INFN. Over almost 5 years of data were taken using\u0000high-purity osmium samples of approximately 173 g. The half-life limits set for\u0000a decays of $^{184}$Os to the first $2^+$ 103.6 keV excited level of $^{180}$W\u0000($T_{1/2} > 9.3 times 10^{15}$ yr) and of $^{186}$Os to the first $2^+$ 100.1\u0000keV of $^{182}$W ($T_{1/2} > 4.8 times 10^{17}$ yr) exceed substantially the\u0000present theoretical predictions that are at level of $T_{1/2} sim (0.6 - 3)\u0000times 10^{15}$ yr for $^{184}$Os and $T_{1/2} sim (0.3 - 2) times 10^{17}$\u0000yr for $^{186}$Os. New half-life limits on the 2EC and EC$beta^+$ decay of\u0000$^{184}$Os to the ground and excited levels of $^{184}$W were set at level of\u0000$T_{1/2} > 10^{16} - 10^{17}$ yr; a lower limit on the $2beta^-$ decay of\u0000$^{192}$Os to the $2^+$ 316.5 keV excited level of $^{192}$Pt was estimated as\u0000$T_{1/2} > 6.1 times 10^{20}$ yr. The half-life limits for $2alpha$ decay of\u0000$^{189}$Os and $^{192}$Os were set for the first time at level of $T_{1/2} >\u000010^{20}$ yr.","PeriodicalId":501206,"journal":{"name":"arXiv - PHYS - Nuclear Experiment","volume":"27 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141507883","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Anomalous soft photons: status and perspectives","authors":"R. Bailhache, D. Bonocore, P. Braun-Munzinger, X. Feal, S. Floerchinger, J. Klein, K. Köhler, P. Lebiedowicz, C. M. Peter, R. Rapp, K. Reygers, W. Schäfer, H. S. Scheid, K. Schweda, J. Stachel, H. van Hees, C. A. van Veen, M. Völkl","doi":"arxiv-2406.17959","DOIUrl":"https://doi.org/arxiv-2406.17959","url":null,"abstract":"This report summarizes the work of the EMMI Rapid Reaction Task Force on\u0000\"Real and Virtual Photon Production at Ultra-Low Transverse Momentum and Low\u0000Mass at the LHC\". We provide an overview of the soft-photon puzzle, i.e., of\u0000the long-standing discrepancy between experimental data and predictions based\u0000on Low's soft-photon theorem, also referred to as \"anomalous\" soft photon\u0000production, and we review the current theoretical understanding of soft\u0000radiation and soft theorems. We also focus on low-mass dileptons as a tool for\u0000determining the electrical conductivity of the medium produced in high-energy\u0000nucleus-nucleus collisions. We discuss how both topics can be addressed with\u0000the planned ALICE 3 detector at the LHC.","PeriodicalId":501206,"journal":{"name":"arXiv - PHYS - Nuclear Experiment","volume":"10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141531540","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Stellar s-process neutron capture cross section of Ce isotopes","authors":"R. N. Sahoo, M. Paul, Y. Kashiv, M. Tessler, M. Friedman, S. Halfon, A. Kreisel, A. Shor, L. Weissman","doi":"arxiv-2406.17646","DOIUrl":"https://doi.org/arxiv-2406.17646","url":null,"abstract":"Stellar abundances of cerium are of high current interest based both on\u0000observations and theoretical models, especially with regard to the\u0000neutron--magic $^{140}$Ce isotope. A large discrepancy of $s-$process stellar\u0000models relative to cerium abundance observed in globular clusters was\u0000highlighted, pointing to possible uncertainties in experimental nuclear\u0000reaction rates. In this work, the stellar neutron capture cross section of the\u0000stable cerium isotopes $^{136}$Ce, $^{138}$Ce, $^{140}$Ce, and $^{142}$Ce, were\u0000re-measured. A $^{nat}$Ce sample was irradiated with quasi-Maxwellian neutrons\u0000at $kT = 34.2$ keV using the $^{7}$Li($p,n$) reaction. The neutron field with\u0000an intensity of $3-5 times 10^{10}$ n/s was produced by irradiating the\u0000liquid-lithium target (LiLiT) with a mA proton beam at an energy (1.92 MeV)\u0000just above the threshold at Soreq Applied Research Accelerator Facility\u0000(SARAF). The activities of the $^{nat}$Ce neutron capture products were\u0000measured using a shielded High Purity Germanium detector. Cross sections were\u0000extracted relative to that of the $^{197}$Au(n,$gamma$) reaction and the\u0000Maxwellian-averaged cross section (MACS) of the Ce isotopes were derived. The\u0000MACS values extracted from this experiment are generally consistent with\u0000previous measurements and show for $^{140}$Ce a value $approx 15$% smaller\u0000than most recent experimental values.","PeriodicalId":501206,"journal":{"name":"arXiv - PHYS - Nuclear Experiment","volume":"53 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141521030","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characterization of isomers produced by the spontaneous fission of ${}^{252}$Cf with the VESPA setup","authors":"V. PiauCEA, DES, IRESNE, DER, Cadarache F-13108 Saint-Paul-Lez-Durance, FranceUniversité Paris-Saclay, CNRS/IN2P3, IJCLab, 91405 Orsay, France, A. GöökDepartment of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden, S. OberstedtEuropean Commission, Joint Research Centre, Directorate for Nuclear Safety and Security, 2440 Geel, Belgium, A. OberstedtExtreme Light Infrastructure - Nuclear Physics, A. ChebboubiCEA, DES, IRESNE, DER, Cadarache F-13108 Saint-Paul-Lez-Durance, France, O. LitaizeCEA, DES, IRESNE, DER, Cadarache F-13108 Saint-Paul-Lez-Durance, France, M. VidaliEuropean Commission, Joint Research Centre, Directorate for Nuclear Safety and Security, 2440 Geel, Belgium","doi":"arxiv-2406.16823","DOIUrl":"https://doi.org/arxiv-2406.16823","url":null,"abstract":"Isomers produced by spontaneous fission of ${}^{252}$Cf have been measured\u0000with the VESPA setup, composed of LaBr$_3$(Ce) detectors for fast $gamma$-ray\u0000spectroscopy and an ionization chamber for detecting fission fragments.\u0000Identification of the isomers was derived from fission\u0000fragment-$gamma$-$gamma$ coincidences. This paper presents the half-life of\u000034 isomeric states measured with this setup, from less than the nanosecond up\u0000to tens of microseconds. Two of these isomers are reported for the first time,\u0000in ${}^{108}$Tc and ${}^{147}$Ce. In addition to this half-life analysis, the\u0000isomers are used to develop and test a nuclear charge calibration of the\u0000ionization chamber.","PeriodicalId":501206,"journal":{"name":"arXiv - PHYS - Nuclear Experiment","volume":"89 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141507884","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comments on the publication \"Discrete symmetries tested at 10e-4 precision using linear polarization of photons from positronium annihilations\" by P. Moskal et al","authors":"E. A. George, T. E. Haugen, O. Naviliat-Cuncic, P. A. Voytas","doi":"arxiv-2406.16228","DOIUrl":"https://doi.org/arxiv-2406.16228","url":null,"abstract":"The authors of Ref.[1] (referred to here as \"Moskal et al.\") claim to have\u0000performed the most precise test of P, T and CP invariance in the decay of\u0000ortho-Positronium. In this note: 1) we demonstrate, assuming standard\u0000properties for Compton scattering, that the average value of the correlation\u0000measured by Moskal et al. must necessarily be zero, independently of any\u0000physics occurring in o-Ps decay; 2) we point out that there is no formal\u0000justification to equate the normal vector to the Compton scattering plane with\u0000the incident photon polarization, as done by Moskal et al.; 3) we observe the\u0000absence of characterization of the device as a Compton polarimeter, which is\u0000paramount in photon polarimetry; 4) we review previous measurements of the\u0000polarization of photons from o-Ps decay, properly implementing the Compton\u0000polarimetry technique, and make the connection with tests of discrete\u0000symmetries; and 5) we stress that the correlation proposed by Moskal et al.\u0000cannot be generated solely by the physics of o-Ps decay, including possible\u0000violations of discrete symmetries.","PeriodicalId":501206,"journal":{"name":"arXiv - PHYS - Nuclear Experiment","volume":"184 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141521037","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Measurement of directed flow in Au+Au collisions at $sqrt{s_{NN}}=$ 19.6 and 27 GeV with the STAR Event Plane Detector","authors":"STAR Collaboration","doi":"arxiv-2406.18213","DOIUrl":"https://doi.org/arxiv-2406.18213","url":null,"abstract":"In heavy-ion collision experiments, the global collectivity of final-state\u0000particles can be quantified by anisotropic flow coefficients ($v_n$). The\u0000first-order flow coefficient, also referred to as the directed flow ($v_{1}$),\u0000describes the collective sideward motion of produced particles and nuclear\u0000fragments in heavy-ion collisions. It carries information on the very early\u0000stage of the collision, especially at large pseudorapidity ($eta$), where it\u0000is believed to be generated during the nuclear passage time. Directed flow\u0000therefore probes the onset of bulk collective dynamics during thermalization,\u0000providing valuable experimental guidance to models of the pre-equilibrium\u0000stage. In 2018, the Event Plane Detector (EPD) was installed in STAR and used\u0000for the Beam Energy Scan phase-II (BES-II) data taking. The combination of EPD\u0000($2.1 <|eta|< 5.1$) and high-statistics BES-II data enables us to extend the\u0000$v_{1}$ measurement to the forward and backward $eta$ regions. In this paper,\u0000we present the measurement of $v_{1}$ over a wide $eta$ range in Au+Au\u0000collisions at $sqrt{s_{NN}}=$ 19.6 and 27 GeV using the STAR EPD. The results\u0000of the analysis at $sqrt{s_{NN}}=$19.6 GeV exhibit excellent consistency with\u0000the previous PHOBOS measurement, while elevating the precision of the overall\u0000measurement. The increased precision of the measurement also revealed finer\u0000structures in heavy-ion collisions, including a potential observation of the\u0000first-order event-plane decorrelation. Multiple physics models were compared to\u0000the experimental results. Only a transport model and a three-fluid hybrid model\u0000can reproduce a sizable $v_{1}$ at large $eta$ as was observed experimentally.\u0000The model comparison also indicates $v_{1}$ at large $eta$ might be sensitive\u0000to the QGP phase transition.","PeriodicalId":501206,"journal":{"name":"arXiv - PHYS - Nuclear Experiment","volume":"19 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141507885","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}