{"title":"$J/psi$ yield enhancement at very low transverse momentum in Pb-Pb collisions at $sqrt{s_mathrm{NN}} = mathrm{5.02 ,TeV}$ with ALICE","authors":"Zhuo Zhou","doi":"10.22323/1.320.0028","DOIUrl":"https://doi.org/10.22323/1.320.0028","url":null,"abstract":"A large excess in the yield of $mathrm{J/psi}$ at very low transverse momentum (${p}_mathrm{T}<mathrm{300 MeV/}c$) and forward rapidity (2.5$<y<$4.0) was recently reported by $mathrm{ALICE}$ using the LHC Run-1 data, in Pb-Pb collisions at $sqrt{s_mathrm{NN}} = mathrm{2.76 ,TeV}$. This is suggestive of coherent $mathrm{J/psi}$ photo-production, similar to measurements in ultra-peripheral collisions (UPC), where the nuclei only interact electromagnetically.During the LHC Run-2, the measurement of the very low ${p}_mathrm{T}$ $mathrm{J/psi}$ at mid-rapidity (-0.9$<y<$0.9) in the di-electron decay channel was possible thanks to the large sample of recorded Pb-Pb collisions. The central barrel detectors provide a good momentum resolution, and make the measurement sensitive to the key characteristics of $mathrm{J/psi}$ coherent photo-production, like the corresponding transverse momentum spectrum.In this talk, it will focus on the $mathrm{J/psi}$ production in the very low-${p}_mathrm{T}$ range in peripheral Pb-Pb collisions at $sqrt{s_mathrm{NN}} = 5.02 ,TeV$. The ${p}_mathrm{T}$ spectrum shape for coherent production will be shown and compared to UPC measurements.","PeriodicalId":104537,"journal":{"name":"Proceedings of 12th International Workshop on High-pT Physics in the RHIC/LHC Era — PoS(High-pT2017)","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131932827","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}
We present an extension of hybrid approach, which combines viscous hydrodynamics, particlization, jet energy loss and hadronic cascade, to describe data in the intermediate and high $p_T$ regimes. This enables us to study mini-jet production and energy loss in heavy ion collisions, in conjunction with the bulk dynamics of QGP fireball. This hybrid approach is applied for Pb-Pb collisions at the LHC with $sqrt{s_{NN}} = 2.76,textrm{TeV}$, and we demonstrate that hadronic re-scatterings have significant effects on mini-jets with intermediate $p_T$.
{"title":"Effects of hadronic rescattering in mini-jet production and energy loss at the LHC","authors":"S. Ryu, Scott Mcdonald, C. Shen, S. Jeon, C. Gale","doi":"10.22323/1.320.0014","DOIUrl":"https://doi.org/10.22323/1.320.0014","url":null,"abstract":"We present an extension of hybrid approach, which combines viscous hydrodynamics, particlization, jet energy loss and hadronic cascade, to describe data in the intermediate and high $p_T$ regimes. This enables us to study mini-jet production and energy loss in heavy ion collisions, in conjunction with the bulk dynamics of QGP fireball. This hybrid approach is applied for Pb-Pb collisions at the LHC with $sqrt{s_{NN}} = 2.76,textrm{TeV}$, and we demonstrate that hadronic re-scatterings have significant effects on mini-jets with intermediate $p_T$.","PeriodicalId":104537,"journal":{"name":"Proceedings of 12th International Workshop on High-pT Physics in the RHIC/LHC Era — PoS(High-pT2017)","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132068122","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}
We present recent progress in the analytical as well as the numerical calculation of the next-to-leading order (NLO) inclusive photon production and photon-jet angular correlations at central rapidities applicable to p+A and p+p collisions. After explaining the general cross section formulae we analyze numerically the different NLO contributions. We quantify the importance of quantum evolution effects for the gluon distribution functions. Finally, we show the results on photon-jet angular harmonics as a probe of gluon saturation effects.
{"title":"Saturation physics with prompt photons at NLO in p+A collisions","authors":"S. Benić, Oscar Garcia-Montero","doi":"10.22323/1.320.0021","DOIUrl":"https://doi.org/10.22323/1.320.0021","url":null,"abstract":"We present recent progress in the analytical as well as the numerical calculation of the next-to-leading order (NLO) inclusive photon production and photon-jet angular correlations at central rapidities applicable to p+A and p+p collisions. After explaining the general cross section formulae we analyze numerically the different NLO contributions. We quantify the importance of quantum evolution effects for the gluon distribution functions. Finally, we show the results on photon-jet angular harmonics as a probe of gluon saturation effects.","PeriodicalId":104537,"journal":{"name":"Proceedings of 12th International Workshop on High-pT Physics in the RHIC/LHC Era — PoS(High-pT2017)","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124790728","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}
A. Ayala, J. D. Castaño-Yepes, C. Dominguez, L. A. Hernandez, S. Hernández-Ortiz, M. Tejeda-Yeomans
We compute prompt photon production from gluon fusion in the presence of a magnetic field in semi-central relativistic heavy-ion collisions. The main ingredient is the treatment of the high gluon density at early stages of the collision where intense magnetic fields are also present. The magnetic field opens new channels for photon production that are forbidden otherwise. The elliptic flow coefficient $v_2$ is also computed. The calculation takes into account the saturation scale and phenomenological factors. Overall, the treatment gives a good description of the excess photon yield and $v_2$, particularly at low values of photon transverse momentum.
{"title":"Impact of the initial high gluon density on the prompt photon yield and $v2$ in heavy-ion collisions with magnetic fields","authors":"A. Ayala, J. D. Castaño-Yepes, C. Dominguez, L. A. Hernandez, S. Hernández-Ortiz, M. Tejeda-Yeomans","doi":"10.22323/1.320.0024","DOIUrl":"https://doi.org/10.22323/1.320.0024","url":null,"abstract":"We compute prompt photon production from gluon fusion in the presence of a magnetic field in semi-central relativistic heavy-ion collisions. The main ingredient is the treatment of the high gluon density at early stages of the collision where intense magnetic fields are also present. The magnetic field opens new channels for photon production that are forbidden otherwise. The elliptic flow coefficient $v_2$ is also computed. The calculation takes into account the saturation scale and phenomenological factors. Overall, the treatment gives a good description of the excess photon yield and $v_2$, particularly at low values of photon transverse momentum.","PeriodicalId":104537,"journal":{"name":"Proceedings of 12th International Workshop on High-pT Physics in the RHIC/LHC Era — PoS(High-pT2017)","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125154006","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}
A. Kurkela, A. Mazeliauskas, J. Paquet, S. Schlichting, D. Teaney
We employ the leading order QCD kinetic theory to describe a consistent matching between the initial stage of a heavy ion collision and the subsequent hydrodynamic evolution. We use the linearized kinetic response functions around the non-equilibirum longitudinally expanding background to map initial energy and momentum perturbations to the energy momentum tensor at hydrodynamic initialization time τ hydro . We check that hadronic observables then become rather insensitive to the cross-over time between kinetic theory and viscous hydrodynamics. The universal scaling of kinetic response in units of kinetic relaxation time allows for a straightforward application of kinetic pre-equilibration event-by-event.
{"title":"Initial conditions for heavy ion collisions with QCD kinetic theory","authors":"A. Kurkela, A. Mazeliauskas, J. Paquet, S. Schlichting, D. Teaney","doi":"10.22323/1.320.0001","DOIUrl":"https://doi.org/10.22323/1.320.0001","url":null,"abstract":"We employ the leading order QCD kinetic theory to describe a consistent matching between \u0000the initial stage of a heavy ion collision and the subsequent hydrodynamic evolution. We use \u0000the linearized kinetic response functions around the non-equilibirum longitudinally expanding \u0000background to map initial energy and momentum perturbations to the energy momentum tensor \u0000at hydrodynamic initialization time τ hydro . We check that hadronic observables then become \u0000rather insensitive to the cross-over time between kinetic theory and viscous hydrodynamics. The \u0000universal scaling of kinetic response in units of kinetic relaxation time allows for a \u0000straightforward application of kinetic pre-equilibration event-by-event.","PeriodicalId":104537,"journal":{"name":"Proceedings of 12th International Workshop on High-pT Physics in the RHIC/LHC Era — PoS(High-pT2017)","volume":"91 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126813276","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}
Physics at forward and backward rapidity in hadron+hadron and nucleus+nucleus collisions give access to kinematic regions that give unique information about nuclear effects from cold nuclear matter, crucial in understanding signals from the final state, such as the Quark Gluon Plasma. This proceedings will focus on three areas of interest. The first will describe a measurement of J/$psi$ suppression in U+U collisions (measured by PHENIX in the forward and backward regions) where signs of regeneration from $coverline{c}$ coalescence are seen. The second will include a measurement and discussion of the effects causing suppression of the $psi$(2s) to $psi$(1s) in cold nuclear matter. Lastly, I will provide an analysis update data taken with a recently added detector to the PHENIX experiment, the MPC-EX that has as its purpose, the measurement of $π^0$s and direct photons in cold nuclear matter at low-x.
{"title":"Overview of PHENIX Physics at Forward and Backward Rapidity","authors":"R. Seto","doi":"10.22323/1.320.0020","DOIUrl":"https://doi.org/10.22323/1.320.0020","url":null,"abstract":"Physics at forward and backward rapidity in hadron+hadron and \u0000 nucleus+nucleus collisions give access to kinematic regions that \u0000 give unique information about nuclear effects from cold nuclear \u0000 matter, crucial in understanding signals from the final state, such \u0000 as the Quark Gluon Plasma. This proceedings will focus on three \u0000 areas of interest. The first will describe a \u0000 measurement of J/$psi$ suppression in U+U collisions (measured by \u0000 PHENIX in the forward and backward regions) where signs of \u0000 regeneration from $coverline{c}$ coalescence are seen. The second \u0000 will include a measurement and discussion of the effects causing \u0000 suppression of the $psi$(2s) to $psi$(1s) in cold nuclear matter. \u0000Lastly, I will provide an analysis update data taken with a recently added detector to the PHENIX \u0000experiment, the MPC-EX that has as its purpose, the measurement of $π^0$s and direct photons in \u0000cold nuclear matter at low-x.","PeriodicalId":104537,"journal":{"name":"Proceedings of 12th International Workshop on High-pT Physics in the RHIC/LHC Era — PoS(High-pT2017)","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134372479","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}
Jet quenching stands out as one of the most striking phenomena measured in heavy-ion collisions. After being discovered at RHIC as a suppression of high-$p_T$ hadrons, with the development of reconstruction techniques capable of dealing with large backgrounds, it has also been confirmed in a wide range of measurements involving fully reconstructed jets. The observed suppression patterns are generally understood as arising from interactions with a color deconfined medium, corroborating the role of jets as probes of the hot and dense matter created in ultrarelativistic heavy-ion collisions. In this proceeding, we report on recent theoretical developments related to how jet fragmentation inside the medium is affected by energy-loss processes. In particular, it is shown how a novel Sudakov suppression factor affects the single-inclusive jet spectrum at high-$p_T$. These developments provide first steps toward a unified theoretical understanding of the quenching of hadrons and jets, accompanied by substructure modifications.
{"title":"High-$p_T$ parton propagation and quenching in the medium","authors":"K. Tywoniuk","doi":"10.22323/1.320.0011","DOIUrl":"https://doi.org/10.22323/1.320.0011","url":null,"abstract":"Jet quenching stands out as one of the most striking phenomena measured in heavy-ion collisions. After being discovered at RHIC as a suppression of high-$p_T$ hadrons, with the development of reconstruction techniques capable of dealing with large backgrounds, it has also been confirmed in a wide range of measurements involving fully reconstructed jets. The observed suppression patterns are generally understood as arising from interactions with a color deconfined medium, corroborating the role of jets as probes of the hot and dense matter created in ultrarelativistic heavy-ion collisions. In this proceeding, we report on recent theoretical developments related to how jet fragmentation inside the medium is affected by energy-loss processes. In particular, it is shown how a novel Sudakov suppression factor affects the single-inclusive jet spectrum at high-$p_T$. These developments provide first steps toward a unified theoretical understanding of the quenching of hadrons and jets, accompanied by substructure modifications.","PeriodicalId":104537,"journal":{"name":"Proceedings of 12th International Workshop on High-pT Physics in the RHIC/LHC Era — PoS(High-pT2017)","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125175308","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":"Jet fragmentation in two-particle correlations in pp, 2 p–Pb and Pb–Pb collisions","authors":"M. Vargyas","doi":"10.22323/1.320.0038","DOIUrl":"https://doi.org/10.22323/1.320.0038","url":null,"abstract":"","PeriodicalId":104537,"journal":{"name":"Proceedings of 12th International Workshop on High-pT Physics in the RHIC/LHC Era — PoS(High-pT2017)","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125146440","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}
We study the color coherence phenomenon starting from the original quark-antiquark antenna laboratory. Firstly, we add a new in-medium hard gluon emission, and after that another one emitted outside it. Describing the decoherence of the $ q bar{q} $ pair through the survival probability, we extract some interesting interpretations in the large-$ N_{c} $ limit. With the purpose of considering a more realistic setting, we address a similar configuration in which a quark-gluon antenna with finite formation time propagates through the medium, and the gluon emits an extra soft gluon afterwards. Finally, we shed light on the role of color coherence in these configurations.
{"title":"Medium induced radiation in multiparton splittings","authors":"V. Vila, F. Dominguez, C. Salgado","doi":"10.22323/1.320.0013","DOIUrl":"https://doi.org/10.22323/1.320.0013","url":null,"abstract":"We study the color coherence phenomenon starting from the original quark-antiquark antenna laboratory. Firstly, we add a new in-medium hard gluon emission, and after that another one emitted outside it. Describing the decoherence of the $ q bar{q} $ pair through the survival probability, we extract some interesting interpretations in the large-$ N_{c} $ limit. With the purpose of considering a more realistic setting, we address a similar configuration in which a quark-gluon antenna with finite formation time propagates through the medium, and the gluon emits an extra soft gluon afterwards. Finally, we shed light on the role of color coherence in these configurations.","PeriodicalId":104537,"journal":{"name":"Proceedings of 12th International Workshop on High-pT Physics in the RHIC/LHC Era — PoS(High-pT2017)","volume":"74 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132389185","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}
Extensive study of heavy ion collisions at RHIC has resulted in discovery of a new state of matter - strongly coupled Quark Gluon Plasma (sQGP). Measurements of high-$p_T$ particles and jets contributes to systematic study of the properties of sQGP. Reconstructed jets are directly associated with partons in the medium, their spectra and nuclear modification factors can be measured up to the high transverse momenta (40 GeV/c at RHIC energies). Yields of leading particles such as $pi^0$ and $eta$ mesons can be measured with high precision at high transverse momenta, which also presents a good opportunity for hard probe measurements. Study of high-$p_T$ observables in different collision systems allows the investigation of the path length dependence of energy loss in the medium. Cu+Au is a first asymmetric heavy ion collision system, available for the analysis. U+U presents an opportunity to research non-spherical heavy ion collision system with highest energy density in central collisions. Non-zero elliptic flow and a hint of suppression of high-$p_T$ hadrons suggests that mini-QGP can be formed in collisions of light and heavy nuclei characterized by high charged particle multiplicities. To address the question of collective behaviour in small systems RHIC provided series of geometry controlled experiments with highly asymmetric systems (p+Au, d+Au, $^3He$+Au). This paper will present the most recent PHENIX results on $pi^0$, $eta$ and reconstructed jets production in various collision systems such as p+Au, d+Au, $^3He$+Au, Cu+Au and U+U. Results will be presented as functions of $p_T$ and centrality.
{"title":"Recent results on high-pT particles and jets from PHENIX experiment","authors":"P. Radzevich","doi":"10.22323/1.320.0007","DOIUrl":"https://doi.org/10.22323/1.320.0007","url":null,"abstract":"Extensive study of heavy ion collisions at RHIC has resulted in discovery of a new state of matter - strongly coupled Quark Gluon Plasma (sQGP). Measurements of high-$p_T$ particles and jets contributes to systematic study of the properties of sQGP. Reconstructed jets are directly associated with partons in the medium, their spectra and nuclear modification factors can be measured up to the high transverse momenta (40 GeV/c at RHIC energies). Yields of leading particles such as $pi^0$ and $eta$ mesons can be measured with high precision at high transverse momenta, which also presents a good opportunity for hard probe measurements. Study of high-$p_T$ observables in different collision systems allows the investigation of the path length dependence of energy loss in the medium. Cu+Au is a first asymmetric heavy ion collision system, available for the analysis. U+U presents an opportunity to research non-spherical heavy ion collision system with highest energy density in central collisions. Non-zero elliptic flow and a hint of suppression of high-$p_T$ hadrons suggests that mini-QGP can be formed in collisions of light and heavy nuclei characterized by high charged particle multiplicities. To address the question of collective behaviour in small systems RHIC provided series of geometry controlled experiments with highly asymmetric systems (p+Au, d+Au, $^3He$+Au). This paper will present the most recent PHENIX results on $pi^0$, $eta$ and reconstructed jets production in various collision systems such as p+Au, d+Au, $^3He$+Au, Cu+Au and U+U. Results will be presented as functions of $p_T$ and centrality.","PeriodicalId":104537,"journal":{"name":"Proceedings of 12th International Workshop on High-pT Physics in the RHIC/LHC Era — PoS(High-pT2017)","volume":"104 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123538359","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}
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