Second year seminar. Massimiliano Marchisone. Torino, 03/05/2013. Università di Torino e INFN Université Blaise Pascal de Clermont-Ferrand et LPC

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1 Second year seminar Massimiliano Marchisone Università di orino e INFN Université Blaise Pascal de Clermont-Ferrand et LPC orino, 03/05/2013 Massimiliano Marchisone, 03/05/2013 Second year seminar, orino 1/31

2 My PhD My PhD is a co-tutoring doctorate between urin and the Blaise Pascal University of Clermont-Ferrand (France). Italian supervisor: Ermanno Vercellin. French supervisor: Pascal Dupieux (+ Xavier Lopez). I spent the rst year of PhD (2011) in urin, the second year (2012) at CERN and now I'm in Clermont-Ferrand. he subject is Analysis of data in PbPb collisions at snn = 2.76 ev with the ALICE Muon Spectrometer. Massimiliano Marchisone, 03/05/2013 Second year seminar, orino 2/31

3 Outline 1 ALICE and the Muon rigger 2 MR performance in PbPb collisions 3 Υ µµ in PbPb collisions 4 Conclusions Massimiliano Marchisone, 03/05/2013 Second year seminar, orino 3/31

4 ALICE and the Muon rigger Massimiliano Marchisone, 03/05/2013 Second year seminar, orino 4/31

5 ALICE and the Muon rigger MR performance in Pb Pb collisions Υ µµ in Pb Pb collisions Conclusions he Quark-Gluon Plasma in heavy-ion collisions Ultrarelativistic heavy-ion collisions are the unique tool to study in laboratory the partonic phase. c Heavy quarks ( and Quark-Gluon Plasma, a decon ned b) are sensitive probes of the properties of the QGP and are abundantly produced at the LHC. Because of their large masses, they are created in hard scattering processes during the early stage of the collision and subsequently interact with the hot and dense medium. Massimiliano Marchisone, 03/05/2013 Second year seminar, orino 5/31

6 Quarkonia in AA collisions Quarkonia play a key role in the study of QGP because: they are created in the early stage of the collision, their production is expected to be modied by the plasma, in a coloured medium, binding forces between partons are screened by other free charges, having dierent radii ( dierent binding energies) a sequential suppression is expected as a function of the energy density (. Matsui and H. Satz, Phys. Lett. B 178 (1986)). Massimiliano Marchisone, 03/05/2013 Second year seminar, orino 6/31

7 A Large Ion Collider Experiment ALICE is the LHC experiment dedicated to the study of heavy-ion collisions at high energies ( s NN = 2.76 ev). It participates also to the LHC pp and ppb program. It is composed by a central barrel, a set of forward detectors and a Muon Spectrometer. Massimiliano Marchisone, 03/05/2013 Second year seminar, orino 7/31

8 he Muon Spectrometer Muon Spectrometer allows the reconstruction of light mesons, quarkonia and open heavy avours in their (di)muon decay. It is composed by a front absorber, a Muon racking system, a magnetic dipole, a muon lter and by a Muon rigger system. In order to reject soft muons from π and K decay, a selection performed by the Muon rigger and based on transverse momentum (p ) is required. Massimiliano Marchisone, 03/05/2013 Second year seminar, orino 8/31

9 he Muon rigger system he rigger system is composed by four planes of 18 Resistive Plate Chambers (RPC) each, a kind of gaseous detector with resistive electrodes. Each RPC is read out by means of copper strips of 1, 2 or 4 cm providing the spatial information. he spatial information is used to estimate the p via the deviation with respect to a straight track from the I.P. Single and dimuon trigger signals above two p cuts are delivered by the Muon rigger system. Massimiliano Marchisone, 03/05/2013 Second year seminar, orino 9/31

10 My work My work can be divided into two parts: rst year: study and analysis of some Muon rigger performance in PbPb collisions, second and third year: analysis of the Υ particle production via the dimuon decay channel in PbPb collisions. Massimiliano Marchisone, 03/05/2013 Second year seminar, orino 10/31

11 MR performance in PbPb collisions Massimiliano Marchisone, 03/05/2013 Second year seminar, orino 11/31

12 ALICE and the Muon rigger MR performance in Pb Pb collisions Υ µµ in Pb Pb collisions Conclusions Muon multiplicity vs centrality Average number of muons per MB event as a function of ll number (i.e. of the time) with a p cut of 0.5 GeV/c. As expected multiplicity of muons increases with the centrality. 0% 10% 1.83 ± % 20% 1.18 ± % 40% 0.62 ± % 80% 0.14 ± 0.01 he stability over the time is satisfactory. Massimiliano Marchisone, 03/05/2013 Second year seminar, orino 12/31

13 ALICE and the Muon rigger MR performance in Pb Pb collisions Υ µµ in Pb Pb collisions Conclusions Strip multiplicity vs centrality Average number of hit strips per MB event as a function of ll number (example of the rst trigger plane, bending direction). 0% 10% 2.93 ± % 20% 1.86 Soft background is not ± % 40% 0.97 ± % 80% 0.21 ± 0.02 included: only hit strips participating in track recognized by the algorithm are taken into account. he di erence with respect to the mean number of muons per event (previous slide) is due to the cluster size. Massimiliano Marchisone, 03/05/2013 Second year seminar, orino 13/31

14 Cluster size: real data he cluster size is the number of adjacent strips which deliver a signal over the discrimination threshold. In the two plots the average cluster size for the four planes of MR for the three strip widths (pp and PbPb collisions). Average values: 1.17 ± 0.01, 1.43 ± 0.02, 2.01 ± For both collisions type the values are the same. Massimiliano Marchisone, 03/05/2013 Second year seminar, orino 14/31

15 Cluster size: Monte Carlo simulation Moreover, I implemented a code for a realistic simulation of cluster size in the Muon rigger. First row: comparison between real data and simulation WIHOU c.s. for three dierent strip widths. Second row: comparison between real data and simulation WIH c.s. for three dierent strip widths. Massimiliano Marchisone, 03/05/2013 Second year seminar, orino 15/31

16 Υ µµ in PbPb collisions Massimiliano Marchisone, 03/05/2013 Second year seminar, orino 16/31

17 Why the Υ? c c and b b states are characterized by dierent binding energy and radius: more bound states have smaller size. he maximum size of a bound state decreases when temperature increases. herefore each resonance has a typical dissociation temperature. One should observe a sequential suppression of the particles: quarkonium is a thermometer of the QGP. here could be opposite eects such as the pairs recombination: at the present LHC energy Υ family is not aected. Massimiliano Marchisone, 03/05/2013 Second year seminar, orino 17/31

18 Nuclear modication factor (R AA ) he goal of this analysis is the extraction of the nuclear modication factor (R AA ). It is a ratio between the Υ yields in PbPb and in pp collisions (with the appropriate normalizations). It could be: = 1: the physics is the same in pp and PbPb collisions, > 1: in PbPb collisions there are some processes that enhance the Υ production, < 1: in PbPb collisions there are some processes that reduce the Υ production with respect to pp. Analytically it can be dened as: dy Υ(1S) dy N Υ(1S) = BR N MB (A ε) y AA is the nuclear overlap function. N MB is the number of MB events in PbPb. σ pp is the cross section in pp for Υ µµ. R AA = dy Υ(1S) dy AA dσ pp dy Massimiliano Marchisone, 03/05/2013 Second year seminar, orino 18/31

19 Data sample he PbPb 2011 data have been analysed: L int = 69 µb 1. All the events satisfy the physics selection and are triggered by the Muon rigger detector. Other cuts on (di)muons have been applied in order to clean the signal and to increase the signicance and the S/B ratio. ) 2 Events/(100 MeV/c Pb Pb s NN = 2.76 ev, L = 69 µb int Centrality: 0% 90% µ 2.5<y<4, p > 2 GeV/c m µ + µ (GeV/c ) Massimiliano Marchisone, 03/05/2013 Second year seminar, orino 19/31

20 Invariant mass spectrum hen, the invariant mass spectrum has been tted with the following functions: a double exponential (α e βx + γ e δx ) for background, a sum of three extended Crystal Ball functions for Υ(1S), Υ(2S) and Υ(3S). Statistics can be divided into two bins of centrality and two of rapidity. ) 2 Events/(100 MeV/c % 90% Pb Pb s NN = 2.76 ev 2.5<y<4 29/04/2013 N ϒ(1S) = 135±20 χ 2 /ndf = N ϒ(2S) = 4±27 m ϒ(1S) = 9.44±0.03 GeV/c 2 N ϒ(3S) = 9±28 σ ϒ(1S) = 143±26 MeV/c m µ (GeV/c ) + µ Massimiliano Marchisone, 03/05/2013 Second year seminar, orino 20/31

21 ε ALICE and the Muon rigger MR performance in PbPb collisions Υ µµ in PbPb collisions Conclusions Monte Carlo simulations A realistic run-by-run simulations have been performed in order to evaluate the acceptance and the eciency of the Muon Spectrometer and to extract the tail parameters of the extended Crystal Ball functions. Generated Υ(1S) are forced to decay into two muons in the acceptance of the spectrometer. 0.5 A Embedding MC ϒ(1S) µ µ in MB Pb Pb collisions at µ 2.5<y<4, p > 2 GeV/c s NN = 2.76 ev 02/05/ Run Other productions have been made to get systematic uncertainties on MC parametrizations. Massimiliano Marchisone, 03/05/2013 Second year seminar, orino 21/31

22 ε ε ε ALICE and the Muon rigger MR performance in PbPb collisions Υ µµ in PbPb collisions Conclusions Monte Carlo simulations 0.3 A /05/ Embedding MC ϒ(1S) µ µ in MB Pb Pb collisions at s NN µ 2.5<y<4, p > 2 GeV/c = 2.76 ev Centrality (%) A 0.35 A /05/ /05/ Embedding MC ϒ(1S) µ µ in MB Pb Pb collisions at s NN = 2.76 ev µ 0% 90%, p >2 GeV/c y Embedding MC ϒ(1S) µ µ in MB Pb Pb collisions at = 2.76 ev ϒ(1S) p (GeV/c) s NN µ 0% 90%, 2.5<y<4, p > 2 GeV/c Massimiliano Marchisone, 03/05/2013 Second year seminar, orino 22/31

23 Summary of systematics Source Centrality Rapidity bkg. description 5%6% U 5%8% U Signal mass position 0.3%1% U 1%6% U extraction signal width 0.3%0.5% U 0.4%1% U tail parameters 1%3% U 2%3% U p DCA cuts 0.2%0.3% U 0.1%0.7% U p and y shapes 5% C 5% U A ε tracking e. 8% C 7%9% U trigger e. 2% C 2% U matching e. 1% C 1% U pp normalization 9% C 9% C reference extrapolation +15% 10% C +9% 7% +25% 14% U N MB 2% C 2% C AA 4% U 4% C C = correlated; U = uncorrelated Massimiliano Marchisone, 03/05/2013 Second year seminar, orino 23/31

24 R AA vs centrality R AA ALICE: Pb-Pb s NN = 2.76 ev, L = 69 µb int Inclusive ϒ(1S), 2.5<y<4, p >0 GeV/c Uncorrelated syst. 20%-90% Correlated syst. 0%-20% Clear Υ(1S) suppression increasing with centrality. Correlated systematics of the same order of the statistical uncertainties N part R AA integrated over rapidity (value±stat.±uncorr.±corr.): 0%-90%: ± 0.065(15%) ± 0.029(7%) (20%) 0.072(16%) 0%-20%: ± 0.075(22%) ± 0.024(7%) (20%) 0.056(16%) 20%-90%: ± 0.121(18%) ± 0.044(7%) (20%) 0.104(16%) Massimiliano Marchisone, 03/05/2013 Second year seminar, orino 24/31

25 R AA vs rapidity R AA ALICE: Pb-Pb s NN = 2.76 ev, L = 69 µb, 0%-90% int Inclusive ϒ(1S), p >0 GeV/c Uncorrelated syst. Correlated syst y No clear rapidity dependence. For 2.5 < y < 3.2: statistical uncertainties larger than the correlated and uncorrelated uncertainties For 3.2 < y < 4.0: statistical and uncorrelated systematics dominate R AA integrated over centrality (value±stat.±uncorr.±corr.): 2.5 < y < 3.2: ± 0.076(18%) (14%) 0.053(13%) ± 0.041(10%) 3.2 < y < 4: ± 0.100(22%) (29%) 0.093(21%) ± 0.042(10%) Massimiliano Marchisone, 03/05/2013 Second year seminar, orino 25/31

26 Comparison with ALICE J/ψ at forward rapidity R AA ALICE: Pb-Pb Inclusive s NN = 2.76 ev, L int ϒ(1S), p >0 GeV/c Inclusive J/ ψ, 0<p <8 GeV/c -1 = 69 µb, 2.5<y<4 Uncorrelated syst. Correlated syst. R AA ALICE: Pb-Pb Inclusive s NN = 2.76 ev, L int ϒ(1S), p >0 GeV/c Inclusive J/ ψ, 0<p <8 GeV/c -1 = 69 µb, 0%-90% Uncorrelated syst. Correlated syst N part y Same data sample and kinematic window. Centrality dependence: seen the large uncertainties, it is dicult to conclude a dierent pattern suppression, results are still in agreement, nevertheless Υ seems more suppressed as compared to J/ψ in central collisions. Rapidity dependence: no dierent behaviour can be observed within the large uncertainties on the Υ(1S) R AA. Massimiliano Marchisone, 03/05/2013 Second year seminar, orino 26/31

27 Comparison with CMS results R AA 1.4 Pb-Pb s NN = 2.76 ev, inclusive ϒ(1S), p >0 GeV/c R AA 1.4 Pb-Pb s NN = 2.76 ev, inclusive ϒ(1S), p >0 GeV/c ALICE: L int CMS: L int -1 = 69 µb, 2.5<y<4-1 = 150 µb, y < ALICE: L int CMS: L int -1 = 69 µb, 0%-90% -1 = 150 µb, 0%-100% Uncorrelated syst. Correlated syst. 0.2 Open: reflected Uncorrelated syst. Correlated syst N part y Comparison with 2011 PbPb CMS data at midrapidity ( y < 2.4), down to p = 0 (PRL 109, (2012)). Centrality dependence: ALICE suppression is compatible with the CMS one. Rapidity dependence (slightly dierent centrality range): the two pattern are compatible, even if the suppression at forward rapidity seems more important. Massimiliano Marchisone, 03/05/2013 Second year seminar, orino 27/31

28 Comparison with theoretical predictions R AA ALICE: Pb-Pb s NN = 2.76 ev, L int Inclusive ϒ(1S), 2.5<y<4, p >0 GeV/c Uncorrelated syst. -1 = 69 µb Correlated syst. R AA Pb-Pb s NN ALICE: L int = 2.76 ev, inclusive ϒ(1S), p >0 GeV/c -1 = 69 µb, 0%-90% -1 CMS: L = 150 µb, 0%-100% int Uncorrelated syst. Correlated syst M. Strickland, arxiv: Boost-invariant plateau Gaussian 4πη/s = 3 4 πη/s = 3 4 πη/s = 2 4 πη/s = 2 4πη/s = 1 4πη/s = N part 0.4 Open: reflected Boost-invariant plateau Gaussian πη/s = 3 4 πη/s = 3 M. Strickland 4 πη/s = 2 4 πη/s = 2 arxiv: πη/s = 1 4πη/s = y heoretical predictions by M. Strickland (arxiv: ). Predictions based on anisotropic hydrodynamics formalism (AHYDRO) which assumes nite local momentum-space anisotropy of the plasma due to nite shear viscosity. wo dierent initial temperature rapidity proles: boost-invariant plateau and Gaussian. For each of them 3 values of 4πη/s. Model doesn't include any initial state eects, nor recombination. Data are reasonably described by the boost-invariant initial temperature prole in case of a shear viscosity of 4πη/s = 1 for both dependences. Massimiliano Marchisone, 03/05/2013 Second year seminar, orino 28/31

29 Conclusions Massimiliano Marchisone, 03/05/2013 Second year seminar, orino 29/31

30 Conclusions and perspectives Concerning the rst part, I demonstrated the good stability of the Muon rigger during time. I evaluated the average cluster size in pp and PbPb collisions: the results are the same. With my new code the cluster size is now well reproduced. Concerning the second part, the analysis is nished. A clear suppression of the Υ(1S) in AA collisions is visible. he results have been compared with other measurements and theoretical predictions. A Public Note is being prepared. Massimiliano Marchisone, 03/05/2013 Second year seminar, orino 30/31

31 Schools, conferences, papers... I participated to the following schools: Bologna (school for GRID users), Otranto (school on nuclear and subnuclear physics), orino (school on particles detectors). And to the following conferences: Physics at LHC (Perugia) with proceeding, Italian Physics Society Congress (L'Aquila), RPC2012 (Frascati) with proceeding, QGP France 2012 (Étretat), LHC France 2013 (Annecy). Several papers already published by the ALICE Collaboration including my name. F. Bossù, M. Gagliardi and M. Marchisone. Performance of the RPC-based ALICE muon trigger system at the LHC. JINS Massimiliano Marchisone, 03/05/2013 Second year seminar, orino 31/31