Jet and bulk observables within a partonic transport approach

Jet and bulk observables within a partonic transport approach Florian Senzel with J. Uphoff, O. Fochler, C. Wesp, Z. Xu and C. Greiner based on Phys.Rev.Lett. 4 (25) 23 Transport meeting, 29.4.25

Outline Motivation 2 The partonic transport model BAMPS 3 Recent results about the...... nuclear modification factor R AA... elliptic flow v 2 and bulk properties... energy loss of reconstructed jets Visualization by Jan Uphoff Visualization framework courtesy MADAI collaboration funded by the NSF under grant NSF-PHY-9-4373 Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting 2 / 3

Motivation Tools for probing QCD matter: Ultra-relativistic heavy-ion collisions by C. Blume Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting 3 / 3

Motivation Collectivity of the bulk regime: Elliptic flow v 2 Fourier decomposition of particle spectra d 3 N p t dp t dydφ (p t, y, φ) = d 2 N 2π p t dp t dy [ + 2v 2(p t, y) cos(2φ) +...] v 2.8.6.4 ideal η/s=.3 η/s=.8 η/s=.6 PHOBOS v n 2 /2.4.2..8.6 v 2 v 3 v 4 v 5 ALICE data v n {2}, p T >.2 GeV η/s =.2.2.4.2 2 3 4 N Part 2 3 4 5 centrality percentile by Romatschke, Phys.Rev.Lett. 99, (27) by Gale et al., Phys.Rev.Lett. (23) State-of-the-art Well described by relativistic (viscous) hydrodynamics Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting 4 / 3

Motivation Jet quenching: Nuclear modification factor R AA Suppression of inclusive particle spectra R AA = d 2 N AA /dp t dy N bin d 2 N pp/dp t dy R AA 2.5 SPS SPS 7.3 GeV (PbPb) π WA98 (-7%) RHIC 2 GeV (AuAu) π ± h PHENIX (-%) STAR (-5%) LHC 2.76 TeV (PbPb) CMS (-5%) ALICE (-5%) GLV: dn g /dy = 4 GLV: dn g /dy = 4 GLV: dn g /dy = 2-4 YaJEM-D elastic, small P esc elastic, large P esc YaJEM ASW 2 PQM: <q> = 3-8 GeV /fm LHC.5 RHIC 2 3 4 2 2 p (GeV/c) T State-of-the-art by CMS Collaboration, Eur. Phys. J. C (22) Well described by perturbative quantum chromodynamics Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting 5 / 3

Motivation Our question: Can perturbative QCD interactions explain in a common framework both the high p t and the bulk medium regime and thereby give microscopical insight into the QGP? pqcd? Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting 6 / 3

The partonic transport model BAMPS The partonic transport model BAMPS BAMPS = Boltzmann Approach to Multi-Parton Scattering Numerical solver for the (3+)D Boltzmann transport equation for partons on the mass-shell: f t + p f E r = C 2 2 + C 2 3 Massless particles (gluons & quarks) Discretized space V and time t: t t P 2 2 = v rel σ 2 2 P 2 3 = v rel σ 2 3 V V P 3 2 = I 3 2 t v rel 8E E 2 E 3 V 2 Test-particles ansatz N test Xu and Greiner, Phys.Rev.C7 (25); Xu and Greiner, Phys.Rev.C76 (27) Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting 7 / 3

The partonic transport model BAMPS Implemented processes - elastic collisions Screened matrix elements M X Y 2 = C X Y 64π 2 αs 2 [t md 2 (αs)]2 s 2 with m 2 D(α s) = d G πα s d 3 p (2π) 3 p (Ncfg + N f f q) LO pqcd cross-sections g g g g g g q q q q g g and q q q q q g q g and q g q g q q q q q q q q and q q q q q q q q and q q q q q(p ) q(p 3 ) g(q) q(p 2 ) q(p 4 ) Uphoff, Fochler, Xu, Greiner: Phys.Rev.C84 (2) Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting 8 / 3

The partonic transport model BAMPS Implemented processes - radiative processes Improved Gunion-Bertsch ME [ ] M X Y +g 2 2 = M X Y 2 48παs ( x) 2 k q k + k 2 (q k ) 2 + md 2 (αs) 2 3 processes g g g g g q g q g g and q g q g g q q q q g q q q q g and q q q q g q q q q g and q q q q g Gunion, Bertsch: Phys.Rev.D25 (982) Fochler, Uphoff, Xu, Greiner: Phys.Rev.D88 (23) q(p ) g(q) q(p 2 ) with x = k e y / s g(k) q(p 3 ) q(p 4 ) Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting 9 / 3

The partonic transport model BAMPS Improved Gunion-Bertsch matrix element dσ/dy (a.u.) 3 25 2 5 exact original GB, without (-x) 2 GB, with (-x) 2, x = k T / s * e y improved GB, with (- x) 2, x = k T / s * e y qq qq g 5-5 -4-3 -2-2 3 4 5 Infrared screening for both GB and exact: θ (cut) = θ ( p i p j λ ). Integration both in GB coordinates and in standard phase space with numeric δ-functions. Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting / 3 y

The partonic transport model BAMPS Running coupling evaluated at the microscopic scale 2 2 processes 2 3 processes α s α s (Q 2 ) with Q 2 {s, t, u} α s α s (Q 2 ) with Q 2 {k t, q t }.5 α s (Q).4.3.2 Deep Inelastic Scattering e + e Annihilation Heavy Quarkonia Bethke, Eur.Phys.J.C64 July 29 Remark Due to universality arguments [], the running coupling can be limited by α s;max =... QCD α s(μ Z) =.84 ±.7 Q [GeV] [] Y. Dokshitzer, Nucl.Phys. A7, (22) Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting / 3

The partonic transport model BAMPS Effective modeling of the LPM effect Issue Coherence effects within a semi-classical approach are not trivial. λ τ f Effective method Parent parton is not allowed to scatter before emitted gluon is formed: M 2 3 2 M 2 3 2 Θ (λ X LPM τ f ) X LPM = X LPM = X LPM (; ) No LPM suppression Only independent scatterings (forbids too many emissions) Allows effectively some collinear gluons Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting 2 / 3

The partonic transport model BAMPS Resulting differential 2 3 cross-sections X LPM =.3 X LPM =. X LPM =.5 X LPM =.3 X LPM =. X LPM =.5 dσ/dk t (arb.units). dσ/dk t (arb.units). s = 24 GeV. s = 2.88 GeV....2.3.4.5 k t / s...2.3.4.5 k t / s X LPM =.3 X LPM =. X LPM =.5 X LPM =.3 X LPM =. X LPM =.5 dσ/dq t (arb.units). dσ/dq t (arb.units).. s = 2.88 GeV. s = 24 GeV...2.3.4.5 q t / s...2.3.4.5 q t / s Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting 3 / 3

The partonic transport model BAMPS Dependence of the differential energy loss on X LPM 3 2.5 T=.4 GeV 2 3, light quark 2 3, charm 2 3, bottom de/dx [GeV/fm] 2.5 α s =.3, κ = E = GeV.5.5.5 2 X Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting 4 / 3

The partonic transport model BAMPS Differential energy loss in a static medium de/dx [GeV/fm] 2.5 2 3, light quark 2 3, charm 2 3, bottom 2 2, light quark 2 2, charm 2 2, bottom running α s, κ = T=.4 GeV.5 2 3 4 5 E [GeV] Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting 5 / 3

The partonic transport model BAMPS From partons to hadronic observables High p t observables Folding with fragmentation functions Di h d 2 N h ( ) pt h = dz d2 N i ( p h ) t Di h dp t dy i z min dp t dy z ( z, Q 2 ), ( z, Q 2) with z = ph t p i t partons i Di h (z, Q 2 ) hadrons h Fragmentation functions by e.g. Albino, Kniehl, Kramer: Nucl.Phys.B83(28) Low p t observables Microscopic hadronization processes are unknown. Assuming parton-hadron duality, the integrated flow is not modified during hadronization. Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting 6 / 3

Results Nuclear modification factor R AA Nuclear modification factor R AA of central HI-collisions R AA.2.8.6.4.2 RHIC BAMPS, neutral pions BAMPS, gluon BAMPS, quark PHENIX, neutral pions, -% Au+Au, s=2 GeV improved GB,X=.3 running coupling ε=.6 GeV/fm 3 b=4.2 fm 5 5 2 p T [GeV] R AA.2.8.6 LHC BAMPS, charged hadrons BAMPS, gluon BAMPS, quark ALICE, charged hadrons, -5% CMS, charged hadrons, -5% PYTHIA initial conditions distributed by Glauber. Pb+Pb, s=2.76 TeV.4 improved GB,X=.3.2 running coupling ε=.6 GeV/fm 3 b=3.6 fm 2 4 6 8 2 4 p T [GeV] After fixing the LPM parameter X LPM =.3 by comparing to RHIC data, BAMPS describes the R AA also at LHC. Suppression caused by the interplay between the improved GB matrix element and the microscopic running coupling. Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting 7 / 3

Results Nuclear modification factor R AA R AA of peripheral HI-collisions R AA.2.8.6 BAMPS, charged hadrons BAMPS, gluon BAMPS, quark ALICE, charged hadrons, -5% CMS, charged hadrons, -5% Pb+Pb, s=2.76 TeV.4 improved GB,X=.3.2 running coupling ε=.6 GeV/fm 3 b=3.6 fm 2 4 6 8 2 4 p T [GeV] R AA 2.8.6.4.2.8.6.4.2 BAMPS, charged hadrons BAMPS, gluon BAMPS, quark ALICE, charged hadrons, 4-5% Pb+Pb, s=2.76 TeV improved GB,X=.3 running coupling ε=.6 GeV/fm 3 b=.3 fm 2 3 4 5 p T [GeV] Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting 8 / 3

Results Nuclear modification factor R AA R AA of central HI collisions for different hadron species R AA.8.6.4.2 Pb Pb, 5%.8.6.4.2 π + +π + p + p + K Charged + K +K p + p + K 2 4 6 8 2 4 6 8 p T.8.6.4.2 Pb Pb, 6 8% 2 4 6 8 2 4 6 8 (GeV/c) ALICE Collaboration, arxiv:4.25 R AA.6.4.2.8.6.4 BAMPS, charged hadrons BAMPS, charged pions BAMPS, charged kaons BAMPS, protons BAMPS, lambdas BAMPS, neutral pions ALICE, charged hadrons, -5% CMS, charged hadrons, -5% Pb+Pb, s=2.76 TeV.2 improved GB,X=.3 ε=.6 GeV/fm 3 running coupling b=3.6 fm 2 3 4 5 6 7 8 p T [GeV] Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting 9 / 3

Results Nuclear modification factor R AA Elliptic flow v 2 (p t ) at high p t v 2 = p 2 x py 2 p 2 t v 2.2.5..5 BAMPS, charged hadrons BAMPS, gluon BAMPS, quark CMS, charged hadrons, 4-5% Pb+Pb, s=2.76 TeV improved GB,X=.3 running coupling ε=.6 GeV/fm 3 b=.3 fm 2 3 4 5 p T [GeV] by B.Betz v 2 (p t > GeV) similar to other pqcd approaches (Betz, Gyulassy: JHEP 48 (24) 9). Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting 2 / 3

Results Bulk observables Integrated elliptic flow v 2 (N part ) RHIC LHC v 2.6.4.2..8.6 BAMPS, parton, X=.3 BAMPS, gluon, X=.3 BAMPS, quark, X=.3 STAR, charged hadrons, v 2 {4} PHOBOS, charged hadrons, track-based PHOBOS, charged hadrons, hit-based Au+Au, s=2 GeV improved GB,X=.3 running coupling ε=.6 GeV/fm 3 v 2.6.4.2..8.6 BAMPS, parton BAMPS, gluon BAMPS, light quark CMS, charged particles, v 2 {4} Pb+Pb, s=2.76 TeV improved GB,X=.3 running coupling ε=.6 GeV/fm 3.4.4.2.2 5 5 2 25 3 35 4 <N part > 5 5 2 25 3 35 4 45 <N part > Same setup with LPM parameter X LPM =.3 leads to a sizable elliptic flow built up in the partonic phase. Attention No hadronization for bulk No hadronic after-burner Missing -2%?! Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting 2 / 3

Results Bulk observables Momentum isotropy of the central region.4.35 RHIC LHC.3 <p z 2 /E 2 >.25.2.5. PYTHIA init.cond. b = fm x T <.5 fm η s <.2.5 2 3 4 5 t[fm] Thermalization pqcd interactions lead to a thermalization time τ fm 2 fm. Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting 22 / 3

Results Bulk observables Macroscopic quantities from microscopic interactions Shear viscosity ratio η/s < α s >, η/s.2.8.6.4 Static medium averaged running coupling < α s >, n f = averaged running coupling < α s >, n f =3 shear viscosity / entropy density η/s, n f = shear viscosity / entropy density η/s, n f =3 Reason for large flow: small shear viscosity over entropy ratio Calculated with Green-Kubo formalism Recent viscous hydro: η/s =.2.2.2.25.3.35.4.45.5.55.6 T [GeV] Running coupling α s (T ) Temperature dependent coupling by microscopically evaluated interactions. Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting 23 / 3

Results Bulk observables Closer look on the distribution of α s in a static medium /N dn/dα s (Q 2 ) 2 8 6 4 T =.2 GeV 2->2, Q 2 = s 2->2, Q 2 = t 2->2, Q 2 = u 2->3, Q 2 = q t 2 2->3, Q 2 = k t 2 <σ trans > 3 2.5 2.5 2->2, α s;max =. 2->2, α s;max =.5 2->2, α s;max = 2. 2->3, α s;max =. 2->3, α s;max =.5 2->3, α s;max = 2. 2.5.5 2 2.5 α s (Q 2 ).5.2.25.3.35.4.45.5.55.6 T [GeV] Distributions of α s (Q 2 ) are broad and have peaks at α s;max. However, due to small momentum transfers the transport cross sections are insensitive to α s;max. Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting 24 / 3

Results Bulk observables Elliptic flow v 2 for different α s;max values v 2.6.4.2..8.6.4.2 BAMPS, partons, α s;max =. BAMPS, partons, α s;max =.5 BAMPS, partons, α s;max =2. STAR, charged hadrons, v 2 {4} PHOBOS, charged hadrons, track-based PHOBOS, charged hadrons, hit-based Au+Au, s=2 GeV improved GB,X=.3 running coupling ε=.6 GeV/fm 3 5 5 2 25 3 35 4 <N part > Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting 25 / 3

Results Reconstructed jets Reconstructed jets in heavy-ion collisions Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting 26 / 3

Results Reconstructed jets Momentum imbalance A J of reconstructed di-jets Definition P(A J ).45.35.25.5.5 A J = p t;leading Jet p t;subleading Jet p t;leading Jet + p t;subleading Jet.4.3.2. PYTHIA, w. smearing BAMPS, w. recoil+back.sub. BAMPS, w/o. recoil+back.sub. CMS, Pb+Pb 2.76TeV -% CMS, p+p 2.76 TeV improved GB,X=.3 running coupl. 2->2, 2->3 p t;cut = GeV b = 3.4 fm Anti-k t, R=.3 p t; > 2 GeV p t;2 > 3 GeV φ > 2 π/3 σ = 2.3 p t..2.3.4.5.6.7.8.9 A J FS, Fochler, Uphoff, Xu, Greiner: arxiv:39.657 Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting 27 / 3

Results Reconstructed jets Jet R AA in comparison with jet R CP data R AA ; R CP.2.8.6.4 BAMPS, jet R AA, R=.2 BAMPS, jet R AA, R=.3 BAMPS, jet R AA, R=.4 ALICE, R CP, (-%/5-8%), R=.2 ATLAS, R CP, (-%/6-8%), R=.2 Pb+Pb, s=2.76 TeV improved GB,X=.3.2 JHEP 43 (24) 3 PLB 79 (23) 22-24 4 6 8 2 4 6 8 pt [GeV] running coupling ε=.6 GeV/fm 3 b=3.6 fm arxiv:52.689 Attention: Preliminary! Quantitative comparison study with jet R AA data is in progress. Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting 28 / 3

Conclusions Conclusions Partonic transport provides means for.. exploring dynamics of the QGP evolution based on pqcd processes. exploring different observables within a common framework. Realistic suppression of jets both at RHIC and LHC. Sizable collective flow within the medium by microscopic pqcd cross sections. Future plans: How does a revisited modeling of the LPM effect change the energy loss and its path-length dependence? More systematic comparison with data! (jet+γ-, jet+h-, h+h-correlations, future collider energies... ) Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting 29 / 3

Conclusions Outlook - R AA of LHC Run 2 R AA.2.8.6.4.2 BAMPS, charged hadrons, s=5.5 TeV BAMPS, gluon, s=5.5 TeV BAMPS, quark, s=5.5 TeV ALICE, charged hadrons, -5% CMS, charged hadrons, -5% Pb+Pb, s=5.5 TeV improved GB,X=.3 running coupling ε=.6 GeV/fm 3 b=. fm 2 4 6 8 2 4 p T [GeV] Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting 29 / 3

Conclusions Conclusions Partonic transport provides means for.. exploring dynamics of the QGP evolution based on pqcd processes. exploring different observables within a common framework. Realistic suppression of jets both at RHIC and LHC. Sizable collective flow within the medium by microscopic pqcd cross sections. Future plans: How does a revisited modeling of the LPM effect change the energy loss and its path-length dependence? More systematic comparison with data! (jet+γ-, jet+h-, h+h-correlations, future collider energies... ) Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting 3 / 3

Backup slides Backup slides Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting 3 / 3

Backup slides Closer look on the role of fragmentation Probability for hadron h with pt h out of parton i with pt i = ph t /z ( ) P i h z, pt h = ( ) d 2 N i ( p h ) t D p h i (z, h Q 2) dp t t dy z d 2 N h dp t dy P h i (z,p th ) 3 2.5 2.5.5 gluon (to GeV ch. hadron) gluon (to 2 GeV ch. hadron) gluon (to 3 GeV ch. hadron) quark (to GeV ch. hadron) quark (to 2 GeV ch. hadron) quark (to 3 GeV ch. hadron) P(p t;hadron ).8.6.4.2 h + +h - from g h + +h - from q 2 4 6 8 2 4 p t;parton 2 3 4 5 6 7 8 9 p t;hadron [GeV] Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting 3 / 3

Backup slides Example: R AA for hadrons with p h t = 3 GeV Hadrons with pt h = 3 GeV stem...... mainly from 6 GeV gluon and 45 GeV quark.... 6 % from gluons and 4 % from quarks. 6 P h i (z,p th ) 3 2.5 2.5.5 gluon (to GeV ch. hadron) gluon (to 2 GeV ch. hadron) gluon (to 3 GeV ch. hadron) quark (to GeV ch. hadron) quark (to 2 GeV ch. hadron) quark (to 3 GeV ch. hadron) P(p t;hadron ).8.6.4.2 h + +h - from g h + +h - from q 2 4 6 8 2 4 p t;parton 2 3 4 5 6 7 8 9 p t;hadron [GeV] Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting 32 / 3

Backup slides Example: R AA for hadrons with p h t = 3 GeV Hadrons with pt h = 3 GeV stem...... mainly from 6 GeV gluon and 45 GeV quark.... 6 % from gluons and 4 % from quarks. 6 R AA.2.8.6 BAMPS, charged hadrons BAMPS, gluon BAMPS, quark ALICE, charged hadrons, -5% CMS, charged hadrons, -5% Pb+Pb, s=2.76 TeV.4 improved GB,X=.3.2 running coupling ε=.6 GeV/fm 3 b=3.6 fm 2 4 6 8 2 4 p T [GeV] RAA h (3 GeV) =.4 Rg AA (6 GeV) +.6 Rq AA (45 GeV).3 Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting 32 / 3

Backup slides Example: Shower event with first recoil partons 8 6 4 z [fm] 2-2 -4-6 -8 8 6 4 x [fm] 2-2 -4-6 8 6 4 2 p t [GeV] -4-6 -2 y [fm] -8 5 Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting 33 / 3

Backup slides Dependence of heavy-ion observables on X LPM R AA.4.2.8.6.4.2 BAMPS, neutral pions, X=.3 BAMPS, gluon, X=.3 BAMPS, quark, X=.3 BAMPS, neutral pions, X=. BAMPS, gluon, X=. BAMPS, quark, X=. PHENIX, neutral pions, -% Au+Au, s=2 GeV improved GB running coupling ε=.6 GeV/fm 3 b=4.2 fm v 2.25.2.5..5 BAMPS, parton, X=.3 BAMPS, gluon, X=.3 BAMPS, quark, X=.3 BAMPS, parton, X=. BAMPS, gluon, X=. BAMPS, quark, X=. STAR, charged hadrons, v 2 {4} PHOBOS, charged hadrons, track-based PHOBOS, charged hadrons, hit-based Au+Au, s=2 GeV improved GB,X=.3 running coupling ε=.6 GeV/fm 3 5 5 2 25 3 35 4 <N part > 5 5 2 p T [GeV] Figure: Elliptic flow v2 of gluons, light quarks, and both together (light partons) within η <. as a function of the number of participants Npart at RHIC for a running coupling and two different LPM parameter X.3,.. As a comparison we show experimental data by STAR and PHOBOS for charged hadrons within η <.5 and η <.. Florian Senzel (Goethe University) Jet and bulk observables within BAMPS Transport meeting 34 / 3