(di-)leptons & heavy flavors in heavy ion collisions at the LHC

Transcription

1 (di-)leptons & heavy flavors in heavy ion collisions at the LHC (di-)leptons & heavy flavors: what is different at the LHC The LHC heavy ion program Selected physics channels quarkonia open heavy flavors low mass dileptons some more exotic channels

2 Recent activities in the field ALICE col. J. Phys. G 30 (2004) 1517; CMS col., CMS NOTE ; ATLAS col., CERN/LHCC/ Hard probes in heavy ion collisions at the LHC 4 working groups (PDF, shadowing and pa; Photons; Heavy quarks and quarkonia; Jet physics) 3 workshops 1 CERN Yellow Report: CERN (493 pages, 308 figures) Heavy quarkonium working group 6 working groups (Spectroscopy; Production; Quarkonium in media; Decays; Standard Model measurements; Future opportunities) 3 workshops 1 CERN Yellow Report: hep-ph/ (521 pages, 260 figures) HERA and the LHC 5 working groups (Parton density functions; Multi-jet final states and energy flow; Heavy quarks (charm and beauty); Diffraction; MC tools) 5 workshops written document in preparation

3 Heavy flavors: what is the LHC central AA large primary production melting of ϒ(1S) by color screening none of the primary J/ψ survives the (PbPb)QGP large secondary production of charmonia kinetic recombination, statistical hadronization, DD annihilation, b-hadron decay hard gluon induced quarkonium breakup hep-ph/ LHC RHIC

4 (di-)leptons: what is the LHC dimuons in ALICE, p µ t > 2 GeV/c unlike-sign total unlike-sign from bottom unlike-sign from charm like-sign from bottom charm pure NLO S.Grigoryan dileptons from b decay dominate the spectrum below ϒ & J/ψ large yield of secondary J/ψ from b decay dileptons from b decay have different origin at low & high mass sizeable yield of like-sign correlated dileptons from b decay

5 Charm(onium) production, suppression, regeneration & in-medium modification interplay between different different time scales charm(onium) carries much more physics than anticipated quenching color screening nuclear absorption parton-(pre)resonance breakup p t broadening parton cascade hard scattering, shadowing kinetic recombination dropping mass, flow increased polarization momentum fluctuations b decay hadronic comovers statistical hadronization systematic studies are a must time DD annihilation

6 How well is the heavy flavor production x-section the LHC? theoretical uncertainties on absolute values: a factor 2-3 theoretical uncertainties on the σ(5.5 TeV)/σ(14 TeV) ratio: few % measuring σ(ccbar, bbbar) in pp 14 TeV is top priority N. Carrer and A. Dainese, hep-ph/

7 On the relevance of measuring σ(b) in pp collisions in the first days σ(b) in pp is mandatory for understanding σ(b) in pa & AA (shadowing, quenching) σ(b) in pp is mandatory for understanding σ(ϒ) in pp, pa & AA (production, absorption, suppression) σ(b) in pp is mandatory for understanding σ(j/ψ) in pp (& pa, AA) (N(b J/ψ)/N(direct J/ψ) ~ 30% in 4π w/o feed-down) open heavy flavor statistics is much larger than quarkonium statistics + N( Υ l l N( bb l ± ) ) % 20% σ(b) = day-one physics in pp the LHC

8 Heavy ion (ALICE) data taking scenario one LHC year = 7 months pp (10 7 s) + few weeks AA (10 6 s), starts in first years: regular pp runs at 14 TeV: commissioning, reference, dedicated pp physics first PbPb run at low luminosity: global observables, large x-sections 2 PbPb runs at high luminosity (L int = 0.5nb -1 /year): small x-sections 1 pa run: structure functions, hadronic reference 1 light ion run: energy density dependence later (different options depending on the first results): pp (or pp-like) at 5.5 TeV other light or intermediate-mass systems other systems p-likea PbPb at low energy PbPb at 5.5 TeV & high luminosity ALICE collaboration, J. Phys. G 30 (2004) 1517

9 Heavy flavor physics LHC (channels investigated so far) charmonia & bottomonia versus centrality transverse momentum system-size reaction plane open bottom (inclusive) cross-section from 2 nd J/ψ, single leptons & dileptons b quark energy loss open charm (exclusive D s) transverse momentum distribution c quark energy loss electron-muon coincidences

10 Heavy the LHC CMS: strong heavy ion program ATLAS: heavy ion LOI (2004) ALICE: the dedicated heavy ion experiment

11 ALICE (A Large Ion Collider Experiment) 1000 members 80 instituts 30 countries HMPID TRD TOF DIPOLE MAGNET L3 MAGNET PMD FMD ITS TPC PHOS MUON FILTER ABSORBER MUON TRACKING CHAMBERS MUON TRIGGER CHAMBERS

12 Heavy flavors with ALICE (di-)electrons: J/ψ, ψ, ϒ, ϒ,ϒ, open charm, open bottom electron-muon coincidences: open charm & bottom hadrons: exclusive D 0 (di-)muons: J/ψ, ψ, ϒ, ϒ,ϒ, open charm, open bottom

13 Heavy flavors with CMS muon spectrometer & silicon tracker in central barrel & end-caps large acceptance, excellent resolution J/ψ, ψ, ϒ, ϒ,ϒ, open charm, open bottom

14 Heavy flavors with ATLAS muon spectrometer & silicon tracker in central barrel & end-caps large acceptance studies limited to ϒ reconstruction & b-jet tagging so far

15 Acceptance for heavy flavor measurements nice complementarity between the 3 experiments ATLAS & CMS acceptance is large in η & limited to high p t ALICE combines hadrons, electrons, muons & covers low p t & high η ATLAS, CMS & ALICE-electrons/hadrons have inner tracking

16 Quarkonium measurements in ATLAS η <1 η <2.5 accep. + efficiency 4.9 % 14.3% resolution (MeV) barrel ( η <1) ϒ & ϒ can be well separated ϒ & ϒ separation is difficult J/ψ studies underway CERN/LHCC/ , L. Rosselet@Vienna04

17 Quarkonium measurements in CMS σm(dimuon) ~ 60 M = 10 GeV in central barrel background mainly coming from uncorrelated muon-pairs J/ψ reconstruction limited to high p t G. Baur et al., CMS NOTE

18 Quarkonium measurements in ALICE acceptance ϒ mass resolution dielectrons p t > 3 GeV/c trigger p t > 3 GeV/c trigger background level 1 = 2 HIJING evts with dn ch /dη = η = 0 each dimuons p t > 2 GeV/c trigger p t > 1 GeV/c trigger J/ψ measurement down to p t = 0 the LHC) resolution allows to separate the 3 ϒ states note: no need for J/ψ trigger (at least in central PbPb collisions)

19 Centrality dependence of quarkonium yields in ALICE-muon cross-sections from R. Vogt in hep-ph/ , assumes neither suppression nor enhancement J/ψ: large stat., good sign. (allows much narrower centrality bins) ψ : small S/B ϒ: good stat., S/B > 1, good sign. ϒ : good stat., S/B > 1, good sign. ϒ : low statistics similar rates for ϒ in the dielectron channel S. Grigoryan (updated Dec. 04)

20 ϒ /ϒ ratio versus p t J.P. Blaizot & J.Y. Ollitrault, Phys. Lett. B 199(1987)499; F. Karsch & H. Satz, Z. Phys. C 51(1991)209; J.F. Gunion & R. Vogt, Nucl. Phys. B 492(1997)301 Melting depends on resonance formation time, dissociation temp. & p t QGP temp., lifetime & size Ratio is flat in pp (CDF) Any deviation from the pp (pa) value is a clear evidence for the QGP (nuclear effects cancel-out) The p t dependence of the ratio is sensitive to the characteristics of the QGP full & realistic simulation error bars = 1 month of central PbPb (10%) E. Dumonteil, PhD Thesis (2004) E. Dumonteil & P. Crochet, ALICE-INT

21 b-hadron cross-section from single muons & unlike-sign dimuons in PbPb UA1 MC method* used by CDF & D0, applied here # to central PbPb (5%) 1) get N b µ from fits with fixed shapes (PYTHIA) & b yield as the only free parameter Mass (GeV/c 2 ) N µµ from bb 41461± ±130 p t (GeV/c) N µ from b ± ± ± ±8 # R. Guernane et al., (2004) *C. Albajar et al., PLB 213 (1988) 405; PLB 256 (1991) 121

22 b-hadron cross-section from single muons & unlike-sign dimuons in PbPb 2) for each µ sample, correct N b µ for eff. & N evt, then convert to hadron cross-section total number of b µ from the fit σ N ( p σ > ( Φ B B min B B min b µ t t ( pt > pt ) = B µ Ldt 1 ε σ p ) ) MC integrated luminosity µ global detection efficiency R. Guernane et al., (2004), C. Albajar et al., PLB 213 (1988) 405; PLB 256 (1991) 121

23 b-hadron cross-section from single muons & unlike-sign dimuons in PbPb 3) the b-hadron inclusive differential cross-section distribution measured data points input distribution input distribution well reconstructed agreement between the 3 channels statistics is (very) large systematic uncertainties underway a nice illustration that one can use Tevatronlike analyzes in PbPb the LHC R. Guernane et al., (2004)

24 Bottom from single electrons with displaced vertices d0 < d0cut: improve S/B for resonances d0 > d0cut: measure electrons from D & B PbPb central (5%) B e ± in ITS/TPC/TRD p t > 2 GeV/c, 200 < d0 < 600 µm e ± from B, S/(S+B) = 90% CERN/LHCC 99-13, R. Turrisi, CERN HIF, 04/13/05

25 b-hadron inclusive differential cross-section from single electrons same method as the one used with (di-)muons plus scenario for b-quark energy loss electrons with 2 < p t < 16 GeV/c b-hadrons with 2 < p t min < 23 GeV/c clear sensitivity to energy loss will be further used to get R AA b-hadrons R AAh, R AA D0 & R AA b-hadrons can be measured simultaneously A. Dainese, nucl-ex/ , nucl-ex/ R. Turrisi CERN HIF, 04/13/05 E-loss calculations: N. Amesto, A. Dainese, C.A. Salgado, U.A. Wiedemann, Phys. Rev. D 71 (2005)

26 From NA50 s (J/ψ)/DY to ALICE s ϒ/bbbar (assuming no quenching on b quarks) w/o ϒ nuclear absorption with ϒ nuclear absorption EPJC 39 (2005) 335 statistics: one month PbPb statistics of the reference is in 5<M<20GeV ~5 times larger than that of the probe errors dominated by uncertainties on ϒ nuclear absorption (~20%) systematic errors underway R. Guernane & S. Grigoryan (2004)

27 The Z 0 as a normalisation to bottomonium suppression most natural normalization to ϒ is b (assuming quenching is under control!) Z 0 : clean signal for normalisation (alternative to Drell-Yan which is out of reach) not an universal normalisation (different shadowing for quarks & gluons) Z 0 in CMS: b-hadron decays dominate the dimuon imass 2 weeks L = cm -2 s -1 : Z 0 µ + µ - in η < 2.5 CMS/NOTE 2001/008

28 Secondary J/ψ from B decay B J/ψ (1S) anything: 1.16 ± 0.10% (PDG) N(direct J/ψ) in central (5%) 5.5 TeV: 0.31 N(bbbar pairs) in central (5%) 5.5 TeV: 4.56 N(b J/ψ) / N(direct J/ψ) = 34% in 4π disentangle primary & secondary J/ψ measure inclusive b cross-section probe b quark in-medium energy loss ALICE: CERN/LHCC 99-13, CMS: CMS/NOTE 2001/008

29 b-hadron cross-section from secondary J/ψ in s = 1960 GeV (CDF results) D. Dacosta et al., Phys. Rev. D 71 (2005)

30 Using secondary J/ψ from B decay to probe b quark energy loss secondary J/ψ from B decay in CMS, p tµ > 5 GeV/c energy loss is modeled in 2 extreme cases: collisional energy loss (minimum) collisional + radiative energy loss (maximum) with energy loss: yield reduced by a factor ~ 4 η distribution gets significantly narrower interest to combine this study with dimuons from b- I.P. Lokhtin & A.M. Snigirev, Eur. Phys. J. C 21(2001)155

31 Low mass dilepton measurements ALICE dielectrons, central PbPb, p t > 1 GeV/c ALICE dimuons, proton-proton, p t > 0.5 GeV/c ALICE dimuons, central PbPb, p t > 1 GeV/c feasible in pp collisions (with p tl > 0.5 GeV/c & with Dalitz rejection in e + e - ) challenging in PbPb collisions (min p tl threshold = 1 GeV/c, trigger & bgd) acceptance limited to high p t excluded in ATLAS & CMS CERN/LHCC 99-13, B. Rapp, PhD thesis

32 Some more exotic channels Secondary J/ψ from tri-muon events in pp w/o 2 nd vertex b measurements from like-sign dileptons electron-muon coincidences Z ± measurements

33 Secondary J/ψ from tri-muon events in pp w/o 2 nd vertex reconstruction dimuon evts in pp, p µ t > 1GeV/c correlated muons correlated muons from b uncorrelated muons dimuon events: 85% of direct J/ψ 15% of J/ψ from b decay tri-muon evts in pp, p µ t > 1GeV/c b-chain S/B = 3 S/ S+B = 80 tri-muon events: 15% of direct J/ψ 85% of J/ψ from b decay doable in pp & pa, very difficult in central ArAr A. Morsch (2004)

34 b measurements from like-sign dileptons 2 sources of like-sign correlated dileptons: like-sign correlated b ~ unlike-sign correlated c B 0 oscillations ~ 30% of total like-sign correlated clean signal (D mesons do not oscillate) signal measurable via (like-sign)-(event-mixing) P. Crochet & P. Braun-Munzinger, Nucl. Instrum. Meth. A 484(2002)564

35 Electron-muon coincidences clean signal covers intermediate rapidities measurement done in ISR (1979!) challenging in heavy ion collisions ALICE-INT

36 W ± measurements with the ALICE muon spectrometer + + q q' W (W ) µ ( µ ) ν µ ( ν µ ) PbPb asymmetries in production & decay due to valence quarks PbPb acceptance PbPb 14 TeV: accep ~ 14 % µ ± /run 5.5TeV: accep ~ 10.8 % µ ± /run background studies underway Z. Conesa del Valle, DIMUONnet 05

37 (di-)leptons & heavy flavors in heavy ion collisions at the LHC new environment, large statistics, new observables, new analyzes rich physics program further possibilities with dileptons B + J/ψ K +, B 0 J/ψ K 0 s, B 0 s J/ψ φ, Λ b J/ψ Λà la CDF & D0 quarkonium & open heavy flavor flow quarkonium polarization dilepton correlations first data in April stay tuned