Quark Matter 2018 Review

Transcription

1 Central China Normal University Institude of Particle Physics Quark Matter 218 Review Ao Luo May 31, 218

2 Content 1 Introduction Jet structure observables Experimental results Some theoretical approaches Jet modification with medium recoil in quarik-gluon plasma Medium response to jet-induced excitation Outlook

3 Introduction 2 Jet-quenching in heavy-ion collisions he interactions between the energetic partons in the jet shower and the QGP medium constituents exchange energies and momenta between them. Leading to the modification of jet structure.

4 Introduction 3 From Yasuki, Fri An increase of relatively soft particle multiplicity is observed at large angles from the jet axis. At the same time the hard component of jets gets narrower.

5 Jet structure 4 How do we look at jets? alk by Y.Chen RAA, AJ Jet mass, zg jet-shape fragment functions

6 Jet structure observables Jet Mass & Z g 5 Groomed shared momentum fraction z g : soft drop : z g min(p 1, p 2 ) > z cut ( R 12 ) β p 1 + p 2 Groomed Jet Mass: R M g 2 p 1µ p µ 2 he reconstructed jet mass is a good probe of medium induced jet modifications and medium response.

7 Jet structure observables Jet fragmentation function & Jet shape 6 ools to study modification of parton shower: Gives info about the dynamics of hot QCD matter. Jet fragmentation function (FF): D(z) 1 N jet dn ch dz, z Jet Shape function (JS): [ ρ(r) = 1 1 N jet jet p jet p ch p jet p jet 2 ] trk (r δr/2,r+δr/2) ptrk δr FF and JS provide different, but complementary info. FF: Longitudinal distribution of momentum. JS: Distribution of jet energy in transverse direction.

8 Jet structure observables alk by Gavin P. Salam, Fri 7 JEWEL+PYHIAarXiv: , by Milhano, Wiedemann and Zapp with medium response

9 Experimental results in jet structure 8 D in jet, J. Wang, ue. Photon-tagged jet FF and shape, K. atar, ue. Jet reconstruction large R, C. McGinn, Wed. Groomed jet mass, Y. Chen, Wed. Jet fragmentation and the angular distributions of charged particles within and around jets, M. Rybar, Wed. So many nice talks, here only show a small part!

10 Inclusive jet shape arxiv: alk by Kaya atar, uesday ρ(r) normalized to unity over r < Enhancement 1 PbPb > A larger fraction of jet energy carried at large distances from the jet axis. Depletion Quark Matter 218

11 Some theoretical approaches 9 JESCAPE 1.: the first software release of the JESCAPE collaboration, Kolja Kauder, Wed. E-by-E jet suppresion, anisotopy and hard-soft tomography, X-N Wang, Wed. Medium response and jet shape modification in quark-gluon plasma, chanwook Park, Wed. Medium response to jet-induced excitation: theory overview, Yasuki achibana, Fri. So many nice talks, here only show a small part!

12 JESCAPE 1. alk by Kauder A new monte carlos event generator, the first release of JESCAPE collaboration. 1

13 Jet modification with medium recoil in QGP alk by Chanwook Park 11 Why we need medium recoil? Jet and medium exchanges energy-momentum. Energy lost by energetic partons may still be within jet cone. Redistributed energy changes jet shape. Energy-momentum of the whole system should be conserved.

14 Recoil in MARINI 12 MARINI Event generator for jet simulation in heavy ion collisions. Compatible with event-by-event 3D hydrodynamic medium.

15 Jet mass and Jet shape with recoil 13 Medium recoil plays an important role in describing jet structure observables. Recoil significantly contributes to the jet shape at larger angles.

16 Medium response theory overview alk by Yasuki achibana, Fri. 14 Models for medium response. Results from recent theoretical studies.

17 Models for medium response alk by Yasuki achibana, Fri. 15 Other models: Hybrid Strong/Weak Coupling Model, AMP, BAMPS, Linearized viscous hydrodynamics with source term...

18 Models: Brief summary alk by Yasuki achibana, Fri. 16

19 Results from recent theoretical studies alk by Yasuki achibana, Fri. 17

20 Results from recent theoretical studies alk by Yasuki achibana, Fri. 18 Medium response significantly contributes to the jet shape at larger angles

21 Results from recent theoretical studies alk by Yasuki achibana, Fri. 19

22 he overall transverse momentum balance and the redistribution of the lost energy from hard jets for asymmetric dijet events in PbPb collisions at 2.76A ev at the LHC is studied within A Multi-Phase ransport (AMP) model. A detailed analysis is performed for the projected transverse momentum /p hard hadrons (p > 8. GeV/c) in both peripheral and central PbPb collisions, while the opposite direction in central collisions is dominated by soft hadrons (p =.5-2. GeV/c). he study of in-cone and out-of-cone contributions to /p mostly emitted at large angles away from the dijet axis. Our AMP calculation is in qualitative agreement with the CMS measurements and the primary mechanism for the energy transported to large angles in the AMP model is the elastic scattering at the partonic stage. Future studies including also inelastic processes should be helpful in understanding the overestimation of the magnitudes of in-cone and out-of-cone imbalances from our AMP calculations, and shed light on different roles played by radiative and collisional processes in the redistribution of the lost energy from hard jets. Jet quenching provides very important evidence for the formation of QGP. It originates from the energy loss experienced by the hard partonic jets initially produced from early scatterings as they traverse and interact with the highly excited nuclear matter created in these energetic collisions. Jet-medium interaction has two important aspects: jet energy loss and the medium response to the lost energy/momentum. he study of jet energy loss has been very successful in the explanation of the suppression of high p hadron and jet productions as well as the nuclear modification of dihadron, dijet, photo-jet and hadron-jet correlations. he search for the signal of the medium response to jet transport has been a long-standing topic: how does the lost energy from the jets evolve with the dynamical medium and where does it show up in the final state particle distributions and correlations? We use the AMP model to study the overall transverse momentum balance and the redistribution of the lost energy from hard jets for asymmetric dijet events. In this work, we use the AMP model with string melting mechanism to simulate PbPb collisions at 2.76A ev using the parameters that have been fitted to describe the soft bulk observables at the LHC energies. here are four main stages in the AMP model: (i) Initial condition. (ii) Parton cascade. (iii) Hadronization. (iv) Hadronicre scattering. he AJ distribution for five different centrality is shown (a) -1% (c) 2-3% (e) 5-1% Fig. 1: AMP flow chart (b) 1-2% (d) 3-5% AMP, σ = 1.5mb AMP, σ = 3.mb CMS p >12GeV/c p >5GeV/c,1,2 φ >2π/3 Anti-k R=.5 1,2 η <2. 1 Fig. 2: R =.5, AJ distribution From peripheral to central collisions, the AJ distribution shifts to the right, indicating energy-loss of the away-side sub-leading jet when traversing through the quark-gluon plasma. [1] Z.-W. Lin, C. M. Ko, B.-A. Li, B. Zhang, and S. Pal, Phys. Rev.C 72, 6491 (25). [2] X.-N.Wang and M. Gyulassy, Phys. Rev. Lett. 68, 148 (1992). [3] CMS-PAS-HIN-14-1 (214), pas.pdf. [4] G. Aad et al. (ALAS Collaboration), Phys. Rev. Lett. 114, 7232 (215). [5] S. Chatrchyan et al. (CMS Collaboration), Phys. Rev. C 84, 2496 (211). [6] J. Xu and C. M. Ko, Phys. Rev. C 83, 3494 (211). [7] M. Cacciari, G. P. Salam, and G. Soyez, Eur. Phys. J. C 72, 1896(212). η <2. 2 One can define the projected transverse momentum: % % PP p i cos (φi φleading jet) % % AMP CMS >8. >.5 P,1>12GeV/c P,2 >5GeV/c φ 1,2 >5π/6 Anti-k R=.3 η 1 <1.6 Fig. 3: R =.3 he overall positive and negative momentum contributions are balanced. From pp, peripheral to central collisions, the increase in negative contribution indicates AJ modification is mainly due to jet quenching. η 2 <1.6 σ=1.5mb A large negative contribution (in the direction of the leading jet) to /p is contributed by hard charged hadrons with high p, while the positive contributions (in the opposite direction of the leading jet) is contributed by soft hadrons with low p. his indicates that a large portion of the lost energy is carried by soft hadrons. Here shows the contributions to /p from different stages in AMP model, with σ = (to mimic pp collisions) and 1.5 mb, for central PbPb collisions, where AJ >.15 (upper) and AJ >.25 (lower) (a) initial state after parton cascade after hadronization after hadronic resc. >.15 Pb+Pb 2.76 ev (-1%) mb (c) p (GeV/c) initial state after parton cascade after hadronization after hadronic resc. >.25 Pb+Pb 2.76 ev (-1%) mb p (GeV/c) (b) >.15 Pb+Pb 2.76 (-1%) 1.5 mb (d) >.25 Pb+Pb 2.76 (-1%) 1.5 mb p (GeV/c) p (GeV/c) Fig. 4: partonic cross section = mb (left) and 1.5 mb (right) he relative contributions in σ = 1.5 mb from different p particles to /p changes dramatically after parton cascade. increases while the contribution from high p particles decreases, which indicates that jet-medium interaction in the partonic stage may give important contribution to the transport of the lost energy from the jets. he hadronic rescattering generates similar though a little smaller effect on /p. he recombination mechanism that converts partons into hadrons produces the opposite effect: the contribution from lower p particles decreases while the contribution from higher p particles increases. Below are contributions for in-cone (left) and out-of-cone (right), central (upper) and peripheral (lower) contributions for two different cone sizes: (a) Pb+Pb 2.76eV -3% R < (c) Pb+Pb 2.76eV 5-1% R < (a) Pb+Pb 2.76eV -3% R < (c) Pb+Pb 2.76eV 5-1% R < (b) Pb+Pb 2.76eV -3% R > >8. > (d) Pb+Pb 2.76eV 5-1% R > Fig. 5: cone size: R= >8. > (b) Pb+Pb 2.76eV -3% R > >8. > R > Fig. 6: cone size: R=1.2 (d) Pb+Pb 2.76eV 5-1% > In-cone contributions are dominated by large p hadrons, while the outof-cone contributions are mostly from small p hadrons. his indicates that a large fraction of the momentum imbalance (partonic energy-loss) is balanced by the soft hadrons at large angles away from the dijet axis. Compared with the CMS data, the AMP overestimates the individual positive and negative contributions to the overall transverse momentum balance (a) Pb+Pb 2.76eV -3% R < (c) Pb+Pb 2.76eV 5-1% R < (b) Pb+Pb 2.76eV -3% R >.8 AMP CMS AMP CMS > >8. > R >.8 Fig. 7: cone size: R=.8 (d) Pb+Pb 2.76eV 5-1% > A possible reason could be that the AMP model neglects radiative processes (the elastic scatterings may be more effective in transporting momentum in the transverse direction than the radiative process which are mostly collinear). (1) Our AMP study shows that the transverse momentum projection /p in the leading jet direction is mainly contributed by hard hadrons (p > 8. GeV/c) in both peripheral and central PbPb collisions, while the opposite direction in central collisions is dominated by soft hadrons (p =.5-2. GeV/c). his suggests that a large fraction of the lost energy from hard jets is carried by the final state soft hadrons. (2) We have investigated the redistribution of the lost energy in the angular direction by dividing the overall momentum balance into in-cone and out-of-cone contributions relative to the dijet axis. he result shows that the soft hadrons which carried the energy are mostly emitted at large angles away from the dijet axis. (3) he AMP model only includes elastic processes, the qualitative agreement of our result with the CMS data might indicate that the elastic collisions are quite effective in the transportation of the lost energy from the hard jets to very large angles. >.5 Medium response via AMP model Poster by Ao Luo 2 [Z.Gao, A.Luo, G-L.Ma, G-Y.Qin,H-Z.Zhang, PRC97,4493, arxiv: ] Search for the signal of the medium response to jet transport. We use AMP model to simulate PbPb collisions at 2.76A ev dijet events. A detailed analysis is performed for /p Overall momentum balance and redistribution of the lost energy in asymmetric dijet events in 2.76A ev Pb-Pb collisions with a multi-phase transport model - [Phys. Rev. C 97, 4493, arxiv: ] Zhan Gao 1, Ao Luo 1, Guo-Liang Ma 2, Guang-You Qin 1, and Han-Zhong Zhang 1 1 Key Laboratory of Quark and Lepton Physics (MOE) and Institute of Particle Physics, Central China Normal University, Wuhan 4379, China 2 Shanghai Institute of Applied Physics, Chinese Academy of Science, Shanghai 218, China Abstract contributed from the final charged hadrons carrying different transverse momenta and emitted from different angular directions. We find that the transverse momentum projection /p in the leading jet direction is mainly contributed by shows that these soft hadrons are Introduction ransverse momentum balance of dijet events Redistribution of the lost energy /p = i p i cos(φ i φ leading jet ) /p i he results suggest that: A large fraction of the lost energy from hard jets is carried by the final state soft hadrons. he soft hadrons which carried the energy are mostly emitted at large angles away from the dijet axis. Our AMP calculation is in qualitative agreement with the CMS data. Event Fraction Event Fraction Event Fraction AMP model Dijet AJ distribution Event Fraction Event Fraction Reference Contributions for different evolution stages he contribution from soft particles to /p Conclusion Compare with CMS data

23 Outlook 21 Investigate the signals of the medium response effect and the redistribution of the lost energy at large angles. Study the jet shape functions with a wide range of r (up to r = 1) for asymmetric dijet events using the AMP model.

24 hanks for your attention!