Monte Carlo activities in ALICE status and prospects Jochen Klein 1 for the ALICE Collaboration 1 CERN 8th International Workshop on Multiple Partonic Interactions at the LHC San Crist´ obal de las Casas, Chiapas, Mexico Nov 28 th – Dec 2 nd , 2016
overview ◮ ALICE overview what’s special about ALICE? ◮ Monte Carlo motivation why ALICE can contribute? ◮ pp and p–Pb results what is new from ALICE? ◮ towards Pb–Pb how can we get more systematic in Pb–Pb? ◮ summary and outlook how can we make further progress? � taking Monte Carlo from pp to Pb–Pb Jochen Klein (CERN) Monte Carlo activities in ALICE MPI @ LHC, Nov/Dec 2016 2 / 19
ALICE detector Jochen Klein (CERN) Monte Carlo activities in ALICE MPI @ LHC, Nov/Dec 2016 3 / 19
ALICE strengths ◮ charged particle tracking over wide p ⊥ range ( ∼ 100 MeV / c − 100 GeV / c ) ◮ excellent particle identification over wide p ⊥ range based on d E / d x , time of flight, RICH; transition radiation and calorimetry for electron identification ◮ full event reconstruction in all available collision systems (pp, p–Pb, Pb–Pb) complementary to other LHC experiments, � gives access to interesting realms of physics Jochen Klein (CERN) Monte Carlo activities in ALICE MPI @ LHC, Nov/Dec 2016 4 / 19
challenging Monte Carlo implementations as experiment we must challenge the implementations of: ◮ underlying event ◮ multiplicity dependence ◮ rope hadronization ◮ colour reconnection ◮ collectivity in small systems ◮ microscopic origin? ◮ thermal model ◮ multi parton interactions ◮ transition from small to large systems experimental constraints � interesting physics to be understood Jochen Klein (CERN) Monte Carlo activities in ALICE MPI @ LHC, Nov/Dec 2016 5 / 19
underlying event (pp) ) Φ 1.6 Toward Region | ∆ φ | < π /3 p > 1.0 GeV/c | η | <0.8 ∆ T η ∆ 1.4 ev ◮ traditional measurement 1/(N 1.2 ch 1 N of underlying event 0.8 0.6 ALICE pp at s = 7 TeV Data (corrected) ◮ particle yield 0.4 Pythia 6 - Perugia 0 0.2 Pythia 8 - Tune 1 Phojet in regions w.r.t. trigger particle 0 RATIO 1.2 ◮ towards 1 0.8 ◮ away 5 10 15 20 25 leading p (GeV/c) ALI-PUB-49790 T ◮ transverse [JHEP 1207 (2012) 116] ������������� ◮ systematic study !" ������ at various energies ���������� ���������� on-going ���� ◮ to be extended with identified particles ◮ important baseline measurement Jochen Klein (CERN) Monte Carlo activities in ALICE MPI @ LHC, Nov/Dec 2016 6 / 19
underlying event (pp) ) Φ Away Region | ∆ φ | > 2 π /3 p > 1.0 GeV/c | η | <0.8 1.2 ∆ T η ∆ ev 1 ◮ traditional measurement 1/(N 0.8 ch N of underlying event 0.6 ALICE pp at s = 7 TeV 0.4 Data (corrected) ◮ particle yield Pythia 6 - Perugia 0 0.2 Pythia 8 - Tune 1 Phojet in regions w.r.t. trigger particle 0 RATIO 1.2 ◮ towards 1 0.8 ◮ away 5 10 15 20 25 leading p (GeV/c) ALI-PUB-49814 T ◮ transverse [JHEP 1207 (2012) 116] ������������� ◮ systematic study !" ������ at various energies ���������� ���������� on-going ���� ◮ to be extended with identified particles ◮ important baseline measurement Jochen Klein (CERN) Monte Carlo activities in ALICE MPI @ LHC, Nov/Dec 2016 6 / 19
underlying event (pp) 0.6 ) Φ Transverse Region π /3 < | ∆ φ | < 2 π /3 p > 1.0 GeV/c | η | <0.8 ∆ T η 0.5 ∆ ev ◮ traditional measurement 1/(N 0.4 ch N 0.3 of underlying event 0.2 ALICE pp at s = 7 TeV Data (corrected) ◮ particle yield 0.1 Pythia 6 - Perugia 0 Pythia 8 - Tune 1 0 Phojet in regions w.r.t. trigger particle RATIO 1.2 ◮ towards 1 0.8 ◮ away 5 10 15 20 25 leading p (GeV/c) ALI-PUB-49802 T ◮ transverse [JHEP 1207 (2012) 116] ������������� ◮ systematic study !" ������ at various energies ���������� ���������� on-going ���� ◮ to be extended with identified particles ◮ important baseline measurement Jochen Klein (CERN) Monte Carlo activities in ALICE MPI @ LHC, Nov/Dec 2016 6 / 19
pseudo-rapidity density (pp) ◮ pp √ s = 13 TeV 9 〉 η ALICE (INEL>0) EPOS LHC /d ch ALICE (INEL) PYTHIA 8 (Monash-2013) ◮ primary particles for N CMS (INEL) PYTHIA 6 (Perugia-2011) d 8 〈 ◮ INEL ◮ INEL > 0 ( | η | < 1) 7 ◮ reasonable agreement with MC, but room for improvement 6 ◮ enters other (more complex) measurements 5 pp, s = 13 TeV − − 2 1 0 1 2 η [PLB 753 (2016) 319-329] Jochen Klein (CERN) Monte Carlo activities in ALICE MPI @ LHC, Nov/Dec 2016 7 / 19
p ⊥ spectra (pp) ◮ pp √ s = 13 TeV ) 2 10 c ALICE, pp, s = 13 TeV, INEL>0 -2 ) (GeV η charged particles, | | < 0.8 1 ◮ INEL > 0 ( | η | < 1) η − 1 10 d T p /(d ◮ Pythia and EPOS show − 2 10 N 2 ) d common patterns of deviation − 3 10 T p π 1/(2 − 4 10 ◮ multiplicity estimator: ev − 5 N 10 meas. N ch in same acceptance: 1/ Data − 6 10 | η | < 0 . 8, EPOS LHC PYTHIA 8 (Monash-2013) − 7 0 . 15 < p ⊥ < 20 GeV / c 10 PYTHIA 6 (Perugia-2011) 1.5 MC / Data ◮ in multiplicity classes, 1 ratio to INEL > 0 Data, systematic uncertainties Data, combined uncertainties 0.5 1 10 p (GeV/ c ) T [PLB 753 (2016) 319-329] Jochen Klein (CERN) Monte Carlo activities in ALICE MPI @ LHC, Nov/Dec 2016 8 / 19
p ⊥ spectra (pp) ◮ pp √ s = 13 TeV 2.2 Ratio to INEL>0 η ALICE, pp, s = 13 TeV, charged particles, | | < 0.8 2 〈 acc 〉 〈 〉 Data, N = 6.7, N = 9.4 ( p > 0.15 GeV/ c ) ch ch T ◮ INEL > 0 ( | η | < 1) ≤ acc 〈 acc 〉 1.8 1 N < N ch ch 〈 acc 〉 ≤ acc 〈 acc 〉 N N < 2 N 1.6 ch ch ch acc acc ≥ 〈 〉 ◮ Pythia and EPOS show N 2 N ch ch 1.4 common patterns of deviation 1.2 1 ◮ multiplicity estimator: 0.8 meas. N ch in same acceptance: 0.6 | η | < 0 . 8, 0.4 MC, selection on N ch 0 . 15 < p ⊥ < 20 GeV / c 〈 〉 EPOS LHC, N = 10.0 0.2 ch 〈 〉 PYTHIA 8 (Monash-2013), N = 10.1 ch 0 ◮ in multiplicity classes, 1 10 p (GeV/ c ) ratio to INEL > 0 T [PLB 753 (2016) 319-329] Jochen Klein (CERN) Monte Carlo activities in ALICE MPI @ LHC, Nov/Dec 2016 8 / 19
multiplicity-dependence of strangeness production (pp) ) ◮ measurement of multiplicity dependence + π + − π 0 of strange particle production ( | y | < 0 . 5) Ratio of yields to ( 2K − 1 S 10 ◮ strangeness enhancement in pp! Λ Λ × + ( 2) effect of strangeness (not mass) + Ξ − Ξ × + ( 6) ◮ Pythia and EPOS are off ◮ DIPSY describes the trend − 2 10 + Ω − Ω × + ( 16) ◮ fundamental origin of strangeness ALICE enhancement not understood; pp, s = 7 TeV p-Pb, s = 5.02 TeV NN only modelled by canonical suppression, Pb-Pb, s = 2.76 TeV NN PYTHIA8 core corona DIPSY EPOS LHC − [1606.07424] 3 10 2 3 10 10 10 〈 η 〉 d N /d η ch | |< 0.5 Jochen Klein (CERN) Monte Carlo activities in ALICE MPI @ LHC, Nov/Dec 2016 9 / 19
centrality dependence of jet spectra (p–Pb) pPb Q Centrality classes (ZNA) ◮ p ⊥ spectra for charged jets: ALICE p-Pb s = 5.02 TeV 1.8 NN 0-20% FastJet anti- k jets, | η | < 0.5 T 20-40% lab 1.6 Reference: scaled pp jets 7 TeV 40-60% anti-kt, | η | < 0 . 5, 60-80% 1.4 80-100% R = 0 . 4 (top), 1.2 1 R = 0 . 2 (bottom) 0.8 0.6 d N c pPb / d p ⊥ 0.4 Q pPb := 0.2 Resolution parameter R = 0.4 � N c coll � d N c pp / d p ⊥ pPb Q Centrality classes (ZNA) ALICE p-Pb s = 5.02 TeV 1.8 NN 0-20% FastJet anti- k jets, | | < 0.5 η T lab 20-40% 1.6 Reference: scaled pp jets 7 TeV ◮ centrality classes from 40-60% 60-80% 1.4 80-100% zero-degree calorimetry, 1.2 1 � avoid dynamical bias 0.8 0.6 ◮ for jets (i.e. hard production) 0.4 0.2 no centrality dependence Resolution parameter R = 0.2 0 20 40 60 80 100 120 p (GeV/ c ) T, ch jet ◮ heavy-ion like behaviour suggested, [EPJC 76 (2016) 5, 271] but jet production not influenced Jochen Klein (CERN) Monte Carlo activities in ALICE MPI @ LHC, Nov/Dec 2016 10 / 19
Recommend
More recommend
