Introduction to WG5: high multiplicities and interactions with nuclei

Transcription

1 8 th International Workshop on Multiple Partonic Interactions at the LHC San Cristóbal de las Casas, Chiapas. November 28, 2016 Introduction to WG5: high multiplicities and interactions with nuclei Antonio Ortiz (ICN, UNAM) and Boris Blok (Technion, Israel)

2 Physics of heavy-ion collisions qthere is experimental evidence that a strongly interacting Quark-Gluon Plasma (sqgp) is formed in ultra-relativistic heavy-ion collisions qthe system is characterized by strong radial and anisotropic flow, as well as opacity to jets (jet quenching) Phys. Rev. Lett. 86 (2001) Phys. Rev. Lett. 88 (2001) November 28, 2016 A. Ortiz (ICN) & B. Blok (Technion) 2

3 Physics of heavy-ion collisions qthere is experimental evidence that a Minimum-bias strongly interacting (MB) pp (and Quark-Gluon p-a) Plasma (sqgp) is formed in ultra-relativistic collisions heavy-ion have initially collisions been used to qthe system is characterized by strong radial provide and benchmarking anisotropic flow, measurements well opacity to jets (jet quenching) for the observations in heavy-ion collisions Phys. Rev. Lett. 86 (2001) Phys. Rev. Lett. 88 (2001) November 28, 2016 A. Ortiz (ICN) & B. Blok (Technion) 3

4 However, MB pp collisions were found to be very interesting The K 0 S transverse momentum spectrum is overestimated by PYTHIA tune ATLAS-CSC and PHOJET below 0.75 GeV/c but is higher by a factor of 2 in the p T range [1-3] GeV/c. We find that strange baryons are significantly under-predicted in both PYTHIA and PHOJET by a factor of 3 ALICE, Eur. Phys. J. C71 (2011) 1594 November 28, 2016 A. Ortiz (ICN) & B. Blok (Technion) 4

5 However, MB pp collisions were found to be very interesting High multiplicity reach, dn ch /dη comparable to that measured in semicentral Cu-Cu collisions JHEP 1101 (2011) November 28, 2016 A. Ortiz (ICN) & B. Blok (Technion) 5

6 However, MB pp collisions were found to be very interesting For increasing N ch, PYTHIA systematically predicts higher jet rates and harder p T spectra than seen in data CMS, Eur. Phys. J. C73 (2013) T S 0.8 soft, p max T < 2 GeV/c 0.8 hard, p max T 2 GeV/c JHEP 1101 (2011) all p-p, s= 7 TeV ALICE PHOJET ATLAS-CSC PERUGIA-0 PERUGIA-2011 Pythia8 ALICE, Eur. Phys. J. C72 (2012) 2124 ATLAS, Phys. Rev. D88 (2013) Data / MC N ch (p 0.5 GeV/c) T N ch (p 0.5 GeV/c) T N ch (p 0.5 GeV/c) T November 28, 2016 A. Ortiz (ICN) & B. Blok (Technion)

7 And the unexpected ridge in pp data CMS, JHEP 09 (2010) 091 CERN CMS seminar summary: Long-range, near side correlation is not seen in low multiplicity events and generators, but resembles effects seen in heavy-ion collisions at high energies November 28, 2016 A. Ortiz (ICN) & B. Blok (Technion) 7

8 And the unexpected ridge in pp data There are many theoretical interpretations of the ridge in pp and p-pb collisions qhydrodynamics q P. Bozek, Eur. Phys. J. C71 (2011) 1530 q K. Werner et al., Phys. Rev. Lett. 106 (2011) q P. Bozek and W. Broniowski, Phys. Lett. B718 (2013) 1557 qsaturation q A. Dumitru et al., Phys. Lett. B697 (2011) q M.G. Ryskin, A.D. Martin and V.A. Khoze, J. Phys. G38 (2011) q K. Dusling and R. Venugopalan, Phys. Rev. Lett. 108 (2012) qother mechanisms q D. d Enterria et al., Eur. Phys. J. C66 (2010) q E. Avsar et al., Phys. Lett. B702 (2011) q Figure taken from: S. Schlichting and P. Tribedy, arxiv: November 28, 2016 A. Ortiz (ICN) & B. Blok (Technion) 8

9 And the unexpected ridge in pp data There are many theoretical interpretations of the ridge in pp and p-pb collisions qhydrodynamics q P. Bozek, Eur. Phys. J. C71 (2011) 1530 q K. Werner et al., Phys. Rev. Lett. 106 (2011) q P. Bozek and W. Broniowski, Phys. Lett. B718 (2013) 1557 qsaturation q Studies of radial flow patterns as a function of the event multiplicity and transverse momentum of the leading jet q A. Dumitru et al., Phys. Lett. B697 (2011) q M.G. Ryskin, q Gyula A.D. Martin Bencedi and V.A. Khoze, J. Phys. G38 (2011) q Event shape dependence of the average q K. Dusling and R. Venugopalan, Phys. Rev. Lett. 108 (2012) p T fluctuations in pp collisions qother mechanisms q Irais Bautista q D. d Enterria et al., Eur. Phys. J. C66 (2010) q E. Avsar et al., Phys. Lett. B702 (2011) q Since high multiplicity events can be also produced by a single high-p T scattering, experimental tools are needed to classify the events: event shapes or jet finders Figure taken from: S. Schlichting and P. Tribedy, arxiv: November 28, 2016 A. Ortiz (ICN) & B. Blok (Technion) 9

10 New developments (using LHC run II data) ATLAS, Phys. Rev. Lett. 116, (2016) November 28, 2016 A. Ortiz (ICN) & B. Blok (Technion) 10

11 New developments (using LHC run II data) 2 < Δη < 5 The collective behavior is usually characterized by cumulants and their Fourier expansions N. Borghini et al., Phys.Rev.C64 (2001) November 28, 2016 A. Ortiz (ICN) & B. Blok (Technion) 11

12 New developments (using LHC run II data) 2 < Δη < 5 Impact on elliptic flow measurements will be presented by q Deepak Kar (ATLAS). Results from other experiments will be covered in the following talks: q Valentina Mariani (CMS) q Zhu Xianglei (LHCb) q Theodore Koblesky (RHIC) November 28, 2016 A. Ortiz (ICN) & B. Blok (Technion) 12

13 Identified particle production ALICE, Phys. Lett. B 760 (2016) 720 Particle ratio ALICE V0A class (Pb-side) 0-5% p-pb = 5.02 TeV ( p + p s NN )/( π π ) Pb-Pb 60-80% s NN INEL pp s = 7 TeV + ( K - + K )/( π + = 2.76 TeV - + π ) More similarities among different colliding systems p T (GeV/c) November 28, 2016 A. Ortiz (ICN) & B. Blok (Technion) 13

14 Identified particle production ALICE, Phys. Lett. B 760 (2016) 720 Particle ratio ALICE V0A class (Pb-side) 0-5% p-pb = 5.02 TeV ( p + p s NN )/( π π p T Radial flow signatures have been observed ) (GeV/c) ALICE, Phys. Lett. B728 (2014) Pb-Pb 60-80% s NN = 2.76 TeV INEL pp s = 7 TeV + ( K - + K )/( π π ) More similarities among different colliding systems November 28, 2016 A. Ortiz (ICN) & B. Blok (Technion) 14

15 Identified particle production Radial flow patterns can be produced by means of multi-parton interactions and color reconnection ALICE, Phys. Lett. PRL B (2013) (2016) Particle ratio ALICE V0A class (Pb-side) 0-5% p-pb = 5.02 TeV ( p + p s NN )/( π π p T Radial flow signatures have been observed ) (GeV/c) ALICE, Phys. Lett. B728 (2014) Pb-Pb 60-80% s NN = 2.76 TeV INEL pp s = 7 TeV + ( K - + K )/( π π ) More similarities among different colliding systems November 28, 2016 A. Ortiz (ICN) & B. Blok (Technion) 15

16 More on identified particle production qstefania Bufalino (ALICE) qvalentina Mariani (CMS) qzhenyu Ye (STAR) qlizardo Valencia (ALICE) November 28, 2016 A. Ortiz (ICN) & B. Blok (Technion) 16

17 More signatures of sqgp in small systems qstrangeness enhancement vs multiplicity in pp and p-pb collisions at the LHC qprabhakar Palni (CCNU) ALICE, arxiv: November 28, 2016 A. Ortiz (ICN) & B. Blok (Technion) 17

18 More signatures of sqgp in small systems qstrangeness enhancement vs multiplicity in pp and p-pb collisions at the LHC qprabhakar Palni (CCNU) ALICE, arxiv: Energy density in small systems close to those reached in heavy-ion collisions. Interesting observation reported by Guy Paić and Eleazar Cuautle arxiv: November 28, 2016 A. Ortiz (ICN) & B. Blok (Technion) 18

19 Thank you November 28, 2016 A. Ortiz (ICN) & B. Blok (Technion) 19