Some surprises in pp p A and AA

Some surprises in pp, p. A and AA high energy collisions Grigory Feofilov St. - Petersburg State University, Faculty of Physics, V. Fock Institute for Physics, Laboratory of Ultra-High Energy Physics “In Search of Fundamental Symmetries”, International Conference dedicated to the Novozhilov's 90 -th anniversary. Saint-Petersburg, December 2 -5, 2014

CONTENT 1. A bit of history 2. Surprises or…what? -- new phenomena in pp collisions at the LHC -- some studies of Pb-Pb collisions with ALICE 2

A bit of history 1998 -- Yu. V is chairing a ceremony at the SPb. SU of Doctor Honoris Causa for Luciano Maiani 3

Yu. V. Novozhilov, L. Maiani and L. A. Verbitskaya 4

A bit of history: SPb. SU in AMPIR collaboration at Moscow Meson Factory – 1987 -1992 1) A. A. Andrianov, A. A. Bolokhov, G. A. Feofilov, V. V. Vereschagin, M. V. loffe, S. N. Manida, M. V. Polyakov, S. G. Sherman, Perspectives of Inelastic Pion Nucleon Scattering Studies at the Detector AMPIR , INES-89, The Proceedings of Internationa 1 Seminar оп Intermediate Energy Physics (USSR, Moscow, 1989, Nov. 27 -30), vо 1. 1, рр. 231 -236, Moscow, 1990. 2) AMPIR collaboration (INR RAS, Kurchatov, SРЬ University), Rare Pion. Nucleon, Pion-Nucleus and {Photonuclear Reaction: Program of Physical Studies at the AMPIR Spectrometer (препринт) Preprint Institut fur Theoretiche Physik Freie Universitat Berlin, FUB-HEP/921, 1990, 21 pages. 3) The Program of investigations of Rare pion-Nucleon reactions and status of AMPIR spectrometer, The Proceedings от Internationa 1 Workshop оп Pions in Nuc 1 ei, Spain, 3 -8 June 1991, Singapour, 1992, рр. 98 -103. …. 5

A bit of history: SPb. SU in ALICE at the LHC -since August 1992 6

Surprise No. 1 – HIGGS! ЦЕРН, 4 июля 2012 ! 7

Standard Model Higgs boson decay branching ratios 8 https: //twiki. cern. ch/twiki/bin/view/LHCPhysics/Cross. Sections#Higgs_cross_sections_and_decay_b

Signal strengths in the main Higgs analysis channels (see review of data in [1]) [1] http: //pdg. lbl. gov/2013/reviews/rpp 2013 -rev-higgs-boson. pdf 9

What about other things@LHC? 10

Surprise No. 2: “Ridge” in pp collisions@LHC Associated Δf Two-particle correlation function: Trigger Signal: Background: Here <N> - number of tracks per event averaged over the multiplicty bin CERN-PH-EP/2010 -031 2010/09/21 12

Near-Side Angular Correlations in Proton-Proton Collisions at the LHC Figure 7: 2 -D two-particle correlation functions for 7 Te. V pp (a) minimum bias events with p. T > 0. 1 Ge. V/c, (b) minimum bias events with 1 < p. T < 3 Ge. V/c, (c) high multiplicity (Noffline trk � 110) events with p. T > 0. 1 Ge. V/c and (d) high multiplicity (Noffline trk � 110) events with 1 < p. T < 3 Ge. V/c. The sharp near-side peak from jet correlations is 13 cut off in order to better illustrate the structure outside that region.

CMC: “Unexplained long-range correlations observed in p. Pb collisions” 14 http: //cms. web. cern. ch/news/unexplained-long-range-correlations-observed-ppb-collisio

Ridge phenomenon in pp and p. Pb collisions is still unexplained… 15

K. Aamodt et al. (ALICE), JINST, 3 , S 08002 (2008) 16 16

Photo: © ALICE: 06. 10. 2020 the Inner Tracking System (ITS) - the Heart of installation (January 2007) 17 17

23 ноября 2009: первое событие в ALICE на LHC! The very 1 st LHC physics paper: “First proton–proton collisions at the LHC as observed with the ALICE detector: measurement of the charged-particle pseudorapidity density at √s = 900 Ge. V“ Eur. Phys. J. C (2010) 65: 111– 125 18

Pb-Pb collisions at the LHC 19

Charged particle pseudo-rapidity density per participant pair for central nucleus-nucleus and non-single diffractive pp (pp) collisions , as a function of √s. NN Ø an increase of about a factor 1. 9 relative to pp collisions at similar collision energies, Ø an increase of about a factor 2. 2 to central Au-Au collisions at √s. NN = 0. 2 Te. V ! Ø Faster growth with √s. NN in AA than in pp! Ø Logarythmic extrapolation is rulled out Ø Important constraint for the models! ar. Xiv: 1011. 3916 [nucl-ex]. Phys. Rev. Lett. 105 (2010) 252301 20 20

Charged-particle multiplicity density at mid-rapidity in central Pb-Pb collisions at √s. NN = 2. 76 Te. V Multiplicity: Ø is essential to estimate the initial energy density and it is the 1 st important constraint for the models! Comparison of ALICE measurement with model predictions. Ø Bjorken energy density: 2. 8 x RHIC for 5% of most central collisions ar. Xiv: 1011. 3916 [nucl-ex]. Phys. Rev. Lett. 105 (2010) 252301 21 21

Charged-particle multiplicity density at mid-rapidity in central Pb-Pb collisions at √s. NN = 2. 76 Te. V: : Empirical extrapolation p. QCD-inspired MC Initial-state gluon density saturation models Some other approaches ] ALICE measurement and model predictions ar. Xiv: 1011. 3916 [nucl-ex]. Phys. Rev. Lett. 105 (2010) 252301 22 22

Centrality dependence of the charged-particle multiplicity density at mid-rapidity in Pb–Pb collisions at √s. NN =2. 76 Te. V Important constraint for the models! ØStrong competition between the models! ØSaturation models {Kharzeev et al. } are looking better … 23 ar. Xiv: 1012. 1657 [nucl-ex], 4 Feb 2011; dx. doi. org/10. 1103/Phys. Rev. Lett. 106. 032301 23

Эллиптический поток в Pb-Pb столкновениях при энергии √s. NN =2. 76 Te. V: Tannebaum’ 06 Excentricity: 2 - and 4 -particle cumulant methods: v 2{2} and v 2{4} ar. Xiv: 1011. 3914 v 1 [nucl-ex] 17 Nov 2010; Phys. Rev. Lett. 105 (2010) 252302 24 24

Surprise: Elliptic flow of charged particles in Pb-Pb collisions at √s. NN =2. 76 Te. V: Integrated elliptic flow vs. centrality ØCERN Press release, November 26, 2010: “…confirms that the much hotter plasma produced at the LHC behaves as a very low viscosity liquid (a perfect fluid)…” Differential elliptic flow vs. pt Øthe value of v 2(pt) does not change within uncertainties from RHIC to LHC Ø Qualitatively similar for all 3 centrality classes. ar. Xiv: 1011. 3914 v 1 [nucl-ex] 17 Nov 2010; Phys. Rev. Lett. 105 (2010) 252302 25 25

Elliptic flow of charged particles in Pb-Pb collisions at √s. NN =2. 76 Te. V: Ø There is a continuous increase in the magnitude of integrated elliptic flow measured in the 20 -30% centrality class from RHIC to LHC energies. ØThis increase is higher than current predictions from ideal hydrodynamic models ar. Xiv: 1011. 3914 v 1 [nucl-ex] 17 Nov 2010; Phys. Rev. Lett. 105 (2010) 252302 26 26

Surprise: Higher harmonic anisotropic flow measurements Initial geometry fluctuations, a mean-free-path (lmf p) and higher harmonics, see: P. Sorensen, ”The rise and fall of the ridge”, Nuclear Physics A 855 (2011) 229– 232 27 27

Higher harmonic anisotropic flow measurements of charged particles in Pb-Pb collisions at √s. NN = 2. 76 Te. V: Intergrated v 2, v 3 and v 4 vs. centrality {2} {4} {2} Øbehavior of higher harmonics is different from that of v 2{2} ! ar. Xiv: 1105. 3865 ; CERN-PH-EP-2011 -073. - 2011 28 28

Higher harmonic anisotropic flow measurements of charged particles in Pb-Pb collisions at √s. NN =2. 76 Te. V: ν 2 , ν 3 , ν 4 , ν 5 vs. pt ν 2 30 -40% centrality ν 3 0 -5% centrality ν 3 ν 2 ar. Xiv: 1105. 3865 ; CERN-PH-EP-2011 -073. - 2011 ν Ø behavior of 3 changes dramatically for very central collisions Øhydrodynamic prediction for v 3(pt) with ƞ/s = 0. 08 better than ƞ/s = 0. 0 Ø no hydro calculation (yet) describing simultaneously data on v 2 and v 3 … …analysis of the viscosity effects is in 29 progress… 29

Suppression of charged particle production at large p. T in central Pb-Pb collisions at √s. NN =2. 76 Te. V: RAA vs. Pt Data driven interpolation 900 Ge. V & 7 Te. V or from NLO 7 Te. V * NLO (2. 76 Te. V)/NLO(7 Te. V) Nuclear modification factor RAA: RAA =1 if no nuclear effects ar. Xiv: 1012. 1004 v 1 [nucl-ex], 5 Dec 2010; Phys. Lett. B 696 (2011) 30 -39 30 30

Suppression of charged particle production at large p. T in central Pb-Pb collisions at √s. NN =2. 76 Te. V: 0. 9 Te. V * NLO (2. 76 Te. V)/NLO(0. 9 Te. V) ØStrong centrality dependence ØSmall losses for peripheral collisions Ø Minimum (~0. 12) is reached at p. T ≈ 6 -7 Ge. V/c Ø Strong rise above 6 Ge. V/c from 0. 9 Te. V * NLO (2. 76 Te. V)/NLO(0. 9 Te. V) ar. Xiv: 1012. 1004 v 1 [nucl-ex], 5 Dec 2010; Phys. Lett. B 696 (2011) 30 -39 31 31

Suppression of charged particle production at large pt in central Pb-Pb collisions at √s. NN =2. 76 Te. V: Øresults are qulitatively similar to the STAR and PHENIX data Ømore “dramatic” behaviour Øthe medium formed in central Pb-Pb collisions is denser than at RHIC ar. Xiv: 1012. 1004 v 1 [nucl-ex], 5 Dec 2010; Phys. Lett. B 696 (2011) 30 -39 32 32

Two-pion Bose--Einstein correlations in central Pb-Pb collisions at √s. NN =2. 76 Te. V: ØHomogeneity-region volume 2 x RHIC (~ d. Nch/dh) 33 ar. Xiv: 1012. 4035 v 2 [nucl-ex]; Phys. Lett. B 696 ( 2011) 328 -337 33

Two-pion Bose--Einstein correlations in central Pb-Pb collisions at √s. NN =2. 76 Te. V: ØDecoupling time tf (~ Rlong) 1. 4 x RHIC (~ (d. Nch/dh)1/3) tf(central Pb. Pb) ~ 10– 11 fm/c 34 ar. Xiv: 1012. 4035 v 2 [nucl-ex]; Phys. Lett. B 696 ( 2011) 328 -337 34

Ongoing analyses : J/psi supression (? ) in Pb-Pb collisions at √s. NN =2. 76 Te. V (preliminary) J/psi production is suppressed (factor ~2) independently on centrality J/psi behavior is still a puzzle …!? 35 35

Summary and outlook ØThe medium produced in Pb-Pb collisions at √s. NN =2. 76 Te. V at the LHC has in comparison to 200 Ge. V data at RHIC: ~ 3 times larger energy density ~ 2 times larger volume of homogenity region ~ Larger lifetime ≈ +20% (≈ 10 fm/c) ØIt shows the properties of almost ideal liquid (like at RHIC) ØIt appears to be denser than at RHIC (suppression of high- pt particles is stronger) Ø J/psi production is suppressed (factor ~2) - still a puzzle…? Ø“Ridge” structures in long-range azimuthal 2 -particle correlations - another puzzle…? We are entering a new and unexplored territory!. . . все самое интересное только начинается! 37 37

BACK-UP slides: 38 38

“Charged-particle multiplicity measurement in proton–proton collisions at √s = 7 Te. V with ALICE at LHC” Fig. 1 Relative increase of the charged-particle pseudorapidity density, for inelastic collisions having at least one charged particle in |η| < 1, between √s = 0. 9 Te. V and 2. 36 Te. V (open squares) and between √s = 0. 9 Te. V and 7 Te. V (full squares), for various models. Corresponding ALICE measurements are shown with vertical dashed and solid lines; the width of shaded bands correspond to the statistical and systematic uncertainties added in quadrature Fig. 2 Charged-particle pseudorapidity density in the central pseudorapidity region |η| < 0. 5 for inelastic and non-single-diffractive collisions [4, 16– 25], and in |η| < 1 for inelastic collisions with at least one charged particle in that region (INEL > 0|η|<1), as a function of the centre-of-mass energy. The lines indicate the fit using a power-la dependence on energy. Note that data points at the same energy have been slightly shifted horizontally for visibility 39 Eur. Phys. J. C (2010) 68: 345– 354

Ongoing analyses : The two-particle azimuthal correlations, higher harmonics and ridges in Pb-Pb at ALICE Pb. Pb central Ø. …the measured anisotropic flow Fourier coefficients give a natural description of these structures… Ø…See also numerous QM-2011 - QM-2014 discussions on higher harmonics Ø…the origin of this effect is still a puzzle… ar. Xiv: 1105. 3865 ; CERN-PH-EP-2011 -073. - 2011 40 40

Отбор центральных событий в эксперименте ALICE Front view of ZDC ZN and ZP calorimeters VZERO: Front view of V 0 A and V 0 C arrays ar. Xiv: 1011. 3916 [nucl-ex]. Phys. Rev. Lett. 105 (2010) 252301 43 43 K. Aamodt et al. (ALICE), JINST, 3 , S 08002 (2008)

Centrality dependence of the charged-particle multiplicity density at mid-rapidity in Pb–Pb collisions at √s. NN =2. 76 Te. V Ø very similar centrality dependence at LHC and RHIC ! (Note 2 scales: “left” (for 2. 76 Te. V and “right” - for 200 Ge. V data) 44 ar. Xiv: 1012. 1657 [nucl-ex], 4 Feb 2011; dx. doi. org/10. 1103/Phys. Rev. Lett. 106. 032301 44

Charged-particle multiplicity density at mid-rapidity in central Pb-Pb collisions at √s. NN = 2. 76 Te. V: : Empirical extrapolation p. QCD-inspired MC Initial-state gluon density saturation models Some other approaches ] ALICE measurement and model predictions ar. Xiv: 1011. 3916 [nucl-ex]. Phys. Rev. Lett. 105 (2010) 252301 45 45

Multiplicity distributions in pp collisions Fig. 3 Measured multiplicity distributions in |η| < 1 for the INEL >0|η|<1 event class. The error bars for data points represent statistical uncertainties, the shaded areas represent systematic uncertainties. Left: The data at the three energies are shown with the NBD fits (lines). Note that for the 2. 36 and 7 Te. V data the distributions have been scaled for clarity by the factors indicated. Right: The data at 7 Te. V are compared to models: PHOJET (solid line), PYTHIA tunes D 6 T (dashed line), ATLAS-CSC (dotted line) and Perugia-0 (dash-dotted line). In the lower part, the ratios between the measured values and model calculations are shown with the same convention. The shaded area represents the combined statistical and systematic uncertainties Eur. Phys. J. C (2010) 68: 345– 354 46

Two photon decay – one of the surprises Feynman diagrams in the Standard Model for the Higgs decay to two photons in lowest order. 47 http: //www. hep. lu. se/atlas/thesis/egede/thesis-node 17. html

Jet Quenching (? ) seen via Multiparticle Correlations d 2 Nch/d. Dhd. Df (signal)/d 2 Nch/d. Dhd. Df (mixed events) • pp Pb ‘Autocorrelation’: d 2 Nch/d. Dhd. Df (signal)/d 2 Nch/d. Dhd. Df (mixed events)Pb. Pb peripheral pp 7 Te. V ‘near side ridge’: Ø- striking effect, not really. CMS understood pp 7 Te. V Ø response of QGP to jet quenching ? ‘near side ridge’ Ø initial state gluon radiation ? Ø ? ? ? Pb. Pb central CERN, 2 Dec 2010 J. Schukraft Pb. Pb central 48 48

Surprise: High p. T Particle Correlations Associated p. Tt ‘near’ side Δf ‘away’ side UE Trigger Particle CERN, 2 Dec 2010 J. Schukraft Trigger Particle: highest p. T particle in event (p. Tt) 49 49 Particle: all the others (p. Ta) Associate

Ongoing analyses : strange and heavy-flavour particle production Signal of decays selected using displaced decay vertices at central rapidity |y|<0/8 (left) and decays in the forward muon spectrometer 2. 5 < y < 4, (right). Pb-Pb collisions, ar. Xiv: 1106. 1341 v 1 [nucl-ex]; 52 52

Ongoing analyses : Prompt D meson Raa RAA (0 -20%) shows a suppression of about a factor of 4 -5 for pt > 5 Ge. V/c Prompt D meson and π+RAA are compatible. Z. Conesa del Valle, report at PANIC, 24 - 29 July 2011, Cambridge, MA, USA 53 53

Подавление J/psi (RHIC) RHIC Au. Au 0. 2 nb-1 Lower Energy CERN-SPS 55

Ongoing analyses : J/psi supression (? ) in Pb-Pb collisions at √s. NN =2. 76 Te. V (preliminary) J/psi production is suppressed (factor ~2) independently on centrality J/psi behavior is still a puzzle …!? 56 56

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