1 Marcello Lunardon - NPDC18, Praha, 2004 Perspectives for the measurement of the beauty production cross section at LHC with ALICE Marcello Lunardon for the ALICE collaboration Phase Transitions in Strongly Interacting Matter PRAHA 2004

2 Marcello Lunardon - NPDC18, Praha, 2004 Contents Why to measure beauty in AA at LHC Performances study for the open beauty detection in Pb-Pb in the semi-electronic channel with ALICE Conclusions and perspectives

3 Marcello Lunardon - NPDC18, Praha, 2004 Measurement of b production in Pb-Pb, p-Pb and p-p Why beauty? B  J/  important background - probe of the medium ( e. g.: energy loss of beauty in the medium to be compared with charm energy loss  study of dead-cone effect ); - discovery potential (new physics window) ! interesting in its own right:

4 Marcello Lunardon - NPDC18, Praha, 2004 Hard processes in AA at the LHC Useful tools: - significant part of the cross section - large virtuality Q  happen at initial time (small “formation time”  t ~ 1/Q << t QGP ~ 5–10 fm/c ) - Initial yields and p t distributions in AA can be predicted using pp measurements + pQCD + collision geometry + “known” nuclear effects  deviations from such predictions can be attributed to the medium path length L c g b energy loss?

5 Marcello Lunardon - NPDC18, Praha, 2004 Study of the nuclear modification factor to get information on the medium Experimental study of energy loss Compare p t distributions of leading particles in pp and nucleus-nucleus collisions (+ p-nucleus as a control) R AA measured at RHIC with pions: clear suppression at high p T interpreted as due to parton energy loss in medium hh What about heavy quarks?

6 Marcello Lunardon - NPDC18, Praha, 2004 – dead cone for heavy quarks: gluons radiation is suppressed at  < m Q /E Q  lower energy loss for heavier partons (Dokshitzer-Kharzeev, 2001) Which energy loss for Heavy Quarks? Yu.L.Dokshitzer and D.E.Kharzeev, Phys. Lett. B519 (2001) 199 [arXiv:hep-ph/ ]. R AA ratio at LHC expected to be less suppressed for heavy flavours because: –D,B come from c,b quarks, while , K, p come mainly (~80% in PYTHIA) from gluons, which are expected to lose  9/4 more energy w.r.t. quarks (due to the difference in the Casimir coupling factor) Expectation for charm: estimated R AA for D 0 mesons at LHC (A. Dainese)  due to the mass dependence of dead cone effect  lower energy loss for beauty compared to charm (Armesto-Dainese-Salgado-Wiedemann, 2004) charmbeauty R AA for electrons from semi-electronic decay of D and B mesons (integrated p T ) N.Armesto, A.Dainese, C.A.Salgado and U.A.Wiedemann, in preparation.

7 Marcello Lunardon - NPDC18, Praha, 2004 The semi-electronic and semi-muonic decay channels have a good B.R.: Open Beauty detection in AA at LHC: the semi-leptonic decay channel B ± /B 0  l + + X10.7 ± 0.3% ( l = e or  ) Good detection and identification capabilities for muons (MUON ARM) and electrons (TRD, TPC and Vertex detector) with ALICE down to low p T (for semi-muonic beauty detection see talk of G. Martinez)

8 Marcello Lunardon - NPDC18, Praha, 2004 X-section from NLO calculations : flavorN qq in 5.5 TeV (5%  tot ) charm115 beauty4.6 in p-p TeV charm0.16 beauty0.007 high uncertainty: Assumption on beauty production at LHC: Open Beauty detection in Pb-Pb at LHC with ALICE: perspectives for the semi-electronic decay channel Semi-electronic channel ~ 10 %, ALICE acceptance for beauty ~ 24 %  in Pb-Pb ~ 0.22 beauty electrons / event Statistics for 10 7 central events (one year Pb-Pb run): ~ 2 M beauty electrons

9 Marcello Lunardon - NPDC18, Praha, 2004 The ALICE Detector ITS Vertexing, Low p t tracking ITS Vertexing, Low p t tracking TPC Tracking, dEdx TPC Tracking, dEdx TRD Electron ID TRD Electron ID L3 Magnet B < 0.5 T: 0.2 T low p t acceptance, 0.5 T p t resolution at high p t L3 Magnet B < 0.5 T: 0.2 T low p t acceptance, 0.5 T p t resolution at high p t The dedicated HI experiment at LHC Designed to measure most observables ITS PIXEL CELL z: 425  m r  : 50  m Two layers: r = 4 – 7 cm 9.8 Mch SPD < 60  m for p t > 1 GeV/c TOF PID TOF PID

10 Marcello Lunardon - NPDC18, Praha, ) electron identification in TRD+TPC Semi-electronic Beauty: detection strategy - track impact parameter in b.p. d 0 long d 0 for beauty electrons due to long B life c  ~ 500  m 2) cuts on - transverse momentum p T B and B products have higher p T than primary particles

11 Marcello Lunardon - NPDC18, Praha, 2004 d 0 and p T distributions for electron from different sources Distributions normalized to the same integral in order to compare their shapes Semi-electronic Beauty: detection strategy

12 Marcello Lunardon - NPDC18, Praha, 2004 Semi-electronic beauty detection: simulation details Most relevant background sources included: 1) hadrons misidentified as electrons 2)  conversions 3) direct charm 4) other decays (Dalitz, strange particles) Separated generation of beauty, charm and background: beauty : Pythia6 with MSEL=5, CTEQ4L, forced semi-electronic decay charm : similar to beauty background : HIJING central (b < 2 fm) events (dN CH /dy| y=0 = 6000) Normalizations according to the NLO cross section calculations Magnetic field: 0.4 T

13 Marcello Lunardon - NPDC18, Praha, 2004 From test beam results: 90% electron efficiency 1% misidentified pions (constant in 1-6 GeV/c p T range) pion contamination ~ 1% Semi-electronic beauty detection background analysis: misidentified pions Electron identification with Transition Radiation Detector (TRD)

14 Marcello Lunardon - NPDC18, Praha, 2004 Combined TRD + TPC particle identification technique brings low momentum pion contamination to less than Semi-electronic beauty detection background analysis: misidentified pions Electron identification with dE/dx in TPC

15 Marcello Lunardon - NPDC18, Praha, 2004 PID used in this simulation: - can assume complete rejection of K,p and heavier particles from TRD and TOF - 80% electron reduction factor for identification efficiencies of TRD (0.9) and TPC (0.9) - pion contamination less than 0.01% at low momentum Semi-electronic beauty detection background analysis: misidentified pions relative magnitudes correct Effect of the PID on the pion backgound Number of pions much greater than number of electrons  good rejection using combined PID technique p T > 1 GeV/c

16 Marcello Lunardon - NPDC18, Praha, 2004 Semi-electronic charm measurement at RHIC from PHENIX: photon conversions are a large part of the background ( have to use a removable converter ) Semi-electronic beauty detection background analysis:  conversions Similar situation expected at ALICE for electrons entering the TPC, but: a) request of 1 st SPD layer b) select positive d 0 electrons a) first reduction asking for first SPD layer

17 Marcello Lunardon - NPDC18, Praha, 2004 Semi-electronic beauty detection background analysis:  conversions b) More reduction with d 0 positive cut

18 Marcello Lunardon - NPDC18, Praha, % semi-electronic decay and much more charm than beauty expected  significant background - softer p T spectrum and d 0 spectrum (c  (D 0 ) ~ 100  m, c  (D + ) ~ 300  m) - separated generation with pythia6 and normalization according with NLO calculations Semi-electronic beauty detection background analysis: direct charm Distributions normalized to the same integral in order to compare their shapes

19 Marcello Lunardon - NPDC18, Praha, 2004 Simulation with HIJING Strange particle decays: low p T but very long d 0  upper d 0 threshold at 600  m Semi-electronic beauty detection background analysis: other decays generally: low p T, low d 0

20 Marcello Lunardon - NPDC18, Praha, 2004 Semi-electronic Beauty detection simulation results Expected statistics (10 7 Pb-Pb events) Signal-to-total ratio and expected statistics in 10 7 Pb-Pb events p T >2 GeV/c, 180  d 0  600  m 90% purity 50,000 B's

21 Marcello Lunardon - NPDC18, Praha, 2004 Analysis of the relative electron sample composition as a function of the electron p T Semi-electronic Beauty detection simulation results Expected statistics (10 7 Pb-Pb events) Direct charm is the most important source of background ( cross check of the extracted c production with direct D 0  K  measurement ) 200  d 0  600  m

22 Marcello Lunardon - NPDC18, Praha, 2004 Example: B  e + D 0 (  K+  ) + X Semi-electronic Beauty detection p T quark distribution Analysis of the electron p T distribution useful for beauty production cross section measurement. But, what about the quark p T distribution? Can get significantly better quark p T distribution if we are able to reconstruct a bigger fraction of the B meson mass.

23 Marcello Lunardon - NPDC18, Praha, 2004 Semi-electronic Beauty detection p T quark distribution Under way: performance study to evaluate - exclusive reconstruction of the D 0 coming from semi-electronic B decay - reconstruction of B secondary vertices using topological variables

24 Marcello Lunardon - NPDC18, Praha, 2004 Summary ALICE has a good potential to measure beauty production cross section ( vertexing and particle identification down to low p T ) this will allow us to extract information about the effect on heavy flavour production of the dense strongly interacting system created in ultra-relativistic heavy-ion collisions Coming up –semi-electronic b/c deconvolution –b’s p t distribution –exclusive b decays

25 Marcello Lunardon - NPDC18, Praha, 2004 THE END

26 Marcello Lunardon - NPDC18, Praha, 2004 BACKUP SLIDES

27 Marcello Lunardon - NPDC18, Praha, 2004 < 60  m for p t > 1 GeV/c 1 % at low p t < 2% up to 10 GeV/c TPC TPC+ITS

28 Marcello Lunardon - NPDC18, Praha, 2004 PID

29 Marcello Lunardon - NPDC18, Praha, 2004

30 LHC: we expect “Deep de-confinement” Lattice QCD,  B =0  closer to “ideal” QGP  easier comparison with theory

31 Marcello Lunardon - NPDC18, Praha, 2004 N.Armesto, A.Dainese, C.A.Salgado and U.A.Wiedemann, in preparation. Energy loss and semi-electronic channel this region could be sensitive to different b/c dead-cone effect charm beauty minimum electron p T

32 Marcello Lunardon - NPDC18, Praha, 2004 D/h ratio: R D/h = R AA D / R AA h Experimentally can use double ratio: R AA D /R AA h –almost all systematic errors of both Pb-Pb and pp cancel out! R D/h is enhanced only by the dead-cone effect Enhancement due to different quark/gluon loss not seen It is compensated by the harder fragmentation of charm

33 Marcello Lunardon - NPDC18, Praha, 2004 Possible direct measurement of  conversions using invariant mass and topological variables

34 Marcello Lunardon - NPDC18, Praha, 2004 Muon Arm simulations: R. Guernane, Muon physics and offline meeting CERN,

35 Marcello Lunardon - NPDC18, Praha, 2004 B measurement a la CDF Simulation by A. Dainese