Federico Antinori (INFN, Padova & CERN, Ginevra) Introduzione alla fisica degli heavy flavour nelle collisioni nucleari ultrarelativistiche Federico Antinori (INFN, Padova & CERN, Ginevra) FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

LHC is a Heavy Flavour Machine! cc and bb rates ALICE PPR (NTLO + shadowing) 115 / 4.6 0.65 / 0.85 6.6 / 0.2 Pb-Pb 5.5 TeV (5% cent) 0.16 / 0.007 1 / 1 11.2 / 0.5 pp 14 TeV shadowing system NN x-sect (mb) total multiplicity cc PbPb/pp bb PbPb/pp PbPb PbPb pp pp FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Probing the medium with heavy flavours c, b produced in early stages of collision, then conserved (neglecting annihilation) production quantitatively under control in pQCD  ideal probes of bulk, strongly interacting phase energy loss? thermal production? no extra production at hadronization  ideal probes of fragmentation independent string fragmentation vs recombination FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Corso in due parti Parte prima: Parte seconda: introduzione heavy flavour in collisioni elementari Parte seconda: heavy flavour in collisioni nucleo-nucleo FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Parte prima : introduzione, heavy flavour in collisioni elementari FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Heavy Flavour Decays FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Some zoology... Lower mass heavy flavour hadrons decay weakly t ~ ps ct ~ 100’s µm weakly decaying states from PDG 2006 summary tables: FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Impact parameter ~ ct in projection: so: In UR limit b ~ Lorentz invariant: ... so b ~ independent of g if cos qCM distribution is flat: so, in space, primary vertex decay vertex decay length = L impact parameter = b q in projection: so: y x d j b FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Weak decays of charm typically: large branching ratio to kaons: D+  K-+X BR ~ 28 % “golden” channel: D+  K-p+p+ BR ~ 9% D0: D0  K-+X BR ~ 50% “golden” channels: D0  K-p+ BR ~ 4% ; D0  K-p+p+p- BR ~ 7% W± branchings: large semileptonic branching ratio, varies with heavy flavour particle, typical ~ 10% ~ 10% heavy flavour hadrons give in final state an e± (and ~ 10% a µ±) (and with a respectable pT...) C = “Cabibbo angle” c s’ W+ u d’ e+ ne µ+ nµ b c W- (similarly: ) FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Standard experimental tools WA92: Si µstrips [Adamovich et al.: NIM A 379 (1996) 252] Silicon vertex detectors: so: tracks from heavy flavour weak decays typically “miss” primary vertex by ct ~ 100’s µm impact parameter resolutions of typical heavy flavour apparatus ~ 10’s µm e± and/or µ ± identification charged kaon identification primary vertex decay vertex decay length = L impact parameter = b q FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Heavy Flavour Production in QCD FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Heavy Flavour hadro-production in pQCD Factorization: (at sufficiently large Q2) hadron hadron charmed hadron parton distribution functions xa = momentum fraction of parton a in hadron A cross-section at parton level e.g.: fragmentation z = fraction of c momentum to hadron D cross-section at hadron level a=q b=q Q FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

factorization implies: PDFs can be measured with one reaction... say: Drell-Yan: A+B  e+e- + X ... and used to calculate a different one say: heavy-flavour production fragmentation independent of the reaction (e.g.: same in pp, e+e-) FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Parton Distribution Functions PDFs vary depending on momentum transfer scale Q2 Intuitively: higher Q2 -> higher resolution high-x parton -> lower-x partons The Q2 evolution of the PDFs can be calculated in pQCD Altarelli-Parisi evolution (DGLAP) FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Leading-order (LO) Relevant diagrams: pair creation qq  QQ (quark-antiquark annihilation) gg  QQ (gluon-gluon fusion) q Q Q g Q g Q g FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

A few results the partonic cross-section decreases with energy faster for qq than for gg (which therefore is expected to dominate, except near threshold) the parton luminosities near threshold increase with energy, the cross section increases with the energy of the hadron-hadron collision the pair cross section is proportional to: y (y): rapidity of Q (Q) Q and Q therefore expected to be close in y Experimentally: EHS, 360 GeV p-p  DDX FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009 [EHS: PLB 123 (1983) 98]

Next-To-Leading-Order (NTLO) in absolute value, LO cross sections are typically underestimated by factor 2.5 - 3 (“K factor”) at NTLO: additional diagrams, such as: Q higher order corrections to pair creation Q flavour excitation Q gluon splitting FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

the agreement with experiment for the total cross-section is good (within large bands...) e.g.: charm cross section at fixed target: FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009 [Mangano: hep-ph/9711337]

results depend on the values of: mc, µR (renormalization scale), µF (factorization scale) the result of an exact calculation would be independent of the choice of the scale parameters µR, µF the residual scale dependence is a measure of the accuracy of the calculation e.g.: for b production at Tevatron (µR=µF=µ): [Mangano: hep-ph/9711337] FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

it is important to match the PDFs with the order of the calculation. e.g. one must avoid double counting: at LO: at NTLO: Q “intrinsic flavour” Q “flavour excitation” FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Heavy Flavour in p/p-A FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Nuclear shadowing PDFs in the nucleus different from PDFs in free proton R = ratio of nuclear to nucleon PDFs from Deep Inelastic Scattering (e-+p; e-+A), Drell-Yan (p+p, p+A -> l +l -+X) e.g.: R for gluons vs gluon momentum fraction x from EKS parametrization [Eskola et al.: EPJ C9 (1999) 61] shadowing antishadowing SPS RHIC LHC typical x for cc production (y  0) x  10-1 @ SPS x  10-2 @ RHIC x  a few 10-4 @ LHC FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Nuclear dependence From pQCD one expects the cross section for production off nuclei to increase like number of nucleon-nucleon collisions (“binary collision scaling”) proportional to number of nucleons (for min. bias collisions): modulo shadowing effects, expected to be small Experimentally: not far... e.g. WA82: D production in p-+W/Si at SPS (340 GeV beam momentum) (relatively) central production with a =1 “Feynman’s x” FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Caveats... i) a = 1 does not work down to pp! e.g.: MacDermott & Reucroft [PLB 184 (1987) 108] compare pA results with earlier hydrogen data from NA27, good agreement using: note: similar situation for light flavours! systematic study by Barton et al. [PRD 27 (1983) 2580], for various reactions at 100 GeV FT e.g.: central for production of p, K, p from p on nuclear targets: with FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

note: a is known to decrease with xF for light hadrons ii) lower a at large xF? early beam dump experiments, sensitive at large xF (max acceptance for xF  0.5) (in tracking experiments, typically max. acceptance for xF  0.2) e.g. WA78 [Cobbaert et al.: PLB 191 (1987) 456] a for muons escaping dump (p-A at 320 GeV FT ): note: a is known to decrease with xF for light hadrons [Barton et al.: PRD 27 (1983) 2580] FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Heavy Flavour Fragmentation FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Fragmentation k  1 GeV/fm String fragmentation model: (e.g. [PYTHIA hep-ph/0308153]) as coloured quarks fly away, energy is stored in the field: above a certain distance it is cheaper to break the string by creating a new qq pair than to keep increasing the distance the string snaps, e.g.: the heavy quark ends up “hadronising” together with a light antiquark the newly created quarks are of course light estimated ratios: u : d : s : c  1 : 1 : 0.3 : 10-11 no heavy flavour production in string breaking! k  1 GeV/fm FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Fragmentation function c  D, D takes fraction z of c momentum fragmentation function: DD/c(z) depends only on fraction z e.g.: Peterson (e = 0.015) Colangelo-Nason (a = 0.9, b=6.4) Peterson Colangelo-Nason e.g.: (parameters from fits to charm production at LEP) FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

How to measure the fragmentation function? we don’t measure the original Q momentum ... but in e+e- we do know the Q momentum (by energy conservation!) e.g.: fragmentation functions are usually extracted from e+e- measurements and then used for other collisions e- Q e+ Z0 FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

e.g.: fits to charm x = 2E/s distributions in e+e-: [Cacciari & Greco: PRD55 (1997) 7134] very similar parameters at the two energies (as expected) Peterson fragmentation s = 10.6 GeV (ARGUS) s = 91.2 GeV (OPAL) e = 0.015 (OPAL) e = 0.019 (ARGUS) FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

e.g. at NTLO a Q can radiate: like for the PDFs, the fragmentation function has to be matched to order of pQCD calculation e.g. at NTLO a Q can radiate: so final energy before non-perturbative part of fragmentation lower than at LO harder fragmentation at NTLO at NTLO: e  0.015 at LO: e  0.06 (e.g.: [Cacciari & Greco: PRD55 (1997) 7134]) Q Peterson fragmentation e = 0.015 (NTLO) e = 0.06 (LO) FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

D* decays, D0(cu) / D+(cd) ratio FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

D* decays Most of the D mesons (from spin counting, ~ 75%) are not directly produced at hadronization, but in D* decays D±, D0 J=0 D*±, D*0 J=1 Due to fine tuning of the values of the masses: m(D±) + m(p0) < m(D*±) m(D0) + m(p±) < m(D*±) m(D0) + m(p0) < m(D*0) but... m(D±) + m(p±) > m(D*0) ... the light quark content of charged D is preserved also in case of resonance decays: a D0(cu) can originate from either D*0(cu) or D*+(cd) a D+(cd) can only originate from a D*+(cd) FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

D0/D+ ratio at LEP D*0 and D*+ both decay strongly into D’s, but: D*+ can decay to both D0 and D+ D*0 can only decay to D0 From spin degeneracy one expects: D0 : D+ : D*0 : D*+ = 1 : 1 : 3 : 3 ... and therefore a large D0/D+ ratio using the experimental branching ratios: but experimentally, at LEP: [ALEPH: EPJ C16 (2000) 597] FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Heavy Flavour at Tevatron FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Beauty at Tevatron Run 0 Run II Discrepancy between pQCD and data seems to have disappeared... from... a factor 5.5 (but only 1.6 s ...) to... Run 0 [CDF: PRL 68 (1992) 3403] Spectrum of J/y from secondary B decays Run II [Cacciari et al: JHEP 0407 (2004)] FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

From run I on, important improvements in accuracy: experiment (vertex detectors, high statistics) prediction (post-HERA PDF sets) Levels of stability over time: no large room for new physics any more... for more see, e.g.: [Cacciari et al: JHEP 0407 (2004) 033, Cacciari: hep-ph/0407187, Mangano: hep-ph/0411020] Data Predictions from [Cacciari et al: JHEP 0407 (2004) 033] FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

What about charm? Nice data from CDF run II roughly in agreement with full pQCD calculation (though prediction somewhat low) [CDF: Phys.Rev.Lett. 91 (2003) 241804] A curiosity (?): good agreement between data and prediction for bare quark [Vogt: talk at SQM 2004] FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Parte seconda : heavy flavour in collisioni nucleo-nucleo FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Charm and beauty: ideal probes study medium with probes of known colour charge and mass e.g.: energy loss by gluon radiation expected to be: parton-specific: stronger for gluons than quarks (colour charge) flavour-specific: stronger for lighter than for heavier quarks (dead-cone effect) study effect of medium on fragmentation (no extra production of c, b at hadronization) independent string fragmentation vs recombination e.g.: D+s/D+ + measurement important for quarkonium physics open QQ production natural normalization for quarkonium studies B meson decays non negligible source of non-prompt J/y FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Heavy flavour production in AA binary scaling: can be broken by: initial state effects (modified PDFs) shadowing kT broadening gluon saturation (colour glass) (concentrated at lower pT) final state effects (modified fragmentation) parton energy loss violations of independent fragmentation (e.g. quark recombination) (at higher pT) FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

What do we know from the SPS? Intermediate mass dimuon excess in central Pb-Pb at SPS (NA50) Main known sources in that region: Drell-Yan and charm pairs M (GeV/c2) central collisions FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Study of the I.M. excess in NA60 Fit weighted impact parameter distribution prompt from J/ψ dimuons, charm from PYTHIA requires > 2 x expected D-Y to fit data NA60 H.Woehri and C.Lourenco, Phys.Rep. 433 (2006) 127-180 6500 A, 2match < 3 sensitivity to assumption on cc pT, Δφ extracted value of cc cross section ~ 2 – 3 larger than extrap. but compatible with extrapolation from NA50 p-A FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Heavy Flavour @ RHIC: experimental techniques FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Non-photonic electrons Identified electron spectra STAR: dE/dx in TPC + TOF at low pT, EMC at high pT PHENIX: combined RICH and E/p (with E from EM cal) Rejection of non-heavy-flavour electrons Main source of electrons: “photonic” g  e+e- conversions Dalitz decays p0  e+e-g Dalitz decays h  e+e-g STAR: rejected by full invariant mass analysis of e+e- combinations PHENIX: estimated by simulation and subtracted (“cocktail method”) measured by “converter method” and subtracted Other sources of non-charm electrons: w, r, j, K decays estimated by sim. and subtracted (in both STAR and PHENIX) (“internal conversions”) FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Reconstructed decays (STAR) D0  K-p+ tracks from TPC K, p identification from dE/dx no separation of D decay vertex large combinatiorial background evaluated by event mixing and subtracted residual background, subtracted with linear fit FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Low pT muons (STAR) m/p in TPC (dE/dx) m/p in TOF [C Zhang (STAR) QM06] m/p in TPC (dE/dx) m/p in TOF fit to impact parameter distribution charm m should ~ point to primary... FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Experimental status FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

PHENIX pp D0 Excess wrt FONLL: Similar situation also in CDF: Ratio: 1.72  0.02 (stat)  0.19 (sys) (0.3 < pT < 9.0 GeV/c) D0 [A. Adare et al. (PHENIX) Phys.Rev.Lett. 97 (2006) 252002] FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009 [D. Acosta et al. (CDF) PRL 91 (2003) 241804]

STAR v PHENIX pp ~ a factor 2 discrepancy [J. Lajoie (PHENIX) QM06] hep-ex/0609010 [J. Lajoie (PHENIX) QM06] FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

STAR dAu, AuAu Internal consistency [M. Calderon (STAR) QM06] FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

STAR v PHENIX dAu, AuAu Discrepancy pretty “stable” v collision system, channel, pT looks like something very basic... of course then RAA not too different... [A. Suaide QM06] FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

STAR v PHENIX: RAA RAA of non-photonic electrons [A. Suaide QM06] similar picture from STAR and PHENIX FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Interpretations FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Theoretically... Energy loss for heavy flavours is expected to be reduced: i) Casimir factor light hadrons originate from a mixture of gluon and quark jets, heavy flavoured hadrons originate from quark jets CR is 4/3 for quarks, 3 for gluons ii) dead-cone effect gluon radiation expected to be suppressed for q < MQ/EQ [Dokshitzer & Karzeev, Phys. Lett. B519 (2001) 199] [Armesto et al., Phys. Rev. D69 (2004) 114003] average energy loss distance travelled in the medium Casimir coupling factor transport coefficient of the medium  R.Baier et al., Nucl. Phys. B483 (1997) 291 (“BDMPS”) FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Experimentally... non ph. el. ~ as suppressed as light hadrons use of high density (qhat), introduction of elastic (in addition to radiative) energy loss... not enough high qhat and no beauty electrons does better [B.I. Abelev et al (STAR): nucl-ex/0607012] FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

How much beauty? high pT region expected to be beauty-dominated [M. Cacciari et al.: PRL 95 (2005) 122001] high pT region expected to be beauty-dominated but how “high”? [A. Suaide QM06] not easy to disentangle c/b contributions to RHIC non ph. el. samples (no heavy flavour vertex detectors in RHIC experiments) FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

E loss being understood? DongJo Kim (PHENIX) FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

another sobering caveat… Relative abundances in charm sector also important: e.g.: Λc/D may change from pp to AA D0 D Ds+ c+ BR (Xe) in % 17.2  1.9 6.71  0.29 8 +6-5 4.5  1.7 c/D (e  c)/(e  D) and what about Ds? s enhancement! Sebastien Gadrat FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009 (see also P Sorensen & X Dong, PRC 74 (2006) 024902)

Vertex Detectors! need less indirect measurement full reconstruction of charm decays! get rid of b/c ambiguities study relative abundances in charm sector Silicon Pixels in ALICE (+ ATLAS, CMS) Silicon Vertex upgrades in STAR, PHENIX FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Track Impact Parameter track impact parameter (d0): separation of secondary tracks from HF decays from primary vtx FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Impact parameter measurement in ALICE ALICE Silicon Pixels PIXEL CELL z: 425 mm rf: 50 mm Two layers: r = 4 cm r = 7 cm  9.8 M expected d0 resolution (s) e.g.: D0  K-p+ FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

LHC is a Heavy Flavour Machine! cc and bb rates ALICE PPR (NTLO + shadowing) 115 / 4.6 0.65 / 0.85 6.6 / 0.2 Pb-Pb 5.5 TeV (5% cent) 0.16 / 0.007 1 / 1 11.2 / 0.5 pp 14 TeV shadowing system NN x-sect (mb) total multiplicity cc PbPb/pp bb PbPb/pp PbPb PbPb pp pp FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

low-x (a field on its own!) large cross-sections low-x (a field on its own!)  accessible x1, x2 regions in the ALICE experiment muon arm central detector FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Heavy Flavour Quenching? some prediction ... charm beauty [Armesto et al.: Phys.Rev. D71 (2005) 054027] FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

D0  K-p+ expected ALICE performance  similar performance in pp S/B ≈ 10 % S/(S+B) ≈ 40 (1 month Pb-Pb running) statistical. systematic.  similar performance in pp (wider primary vertex spread) pT - differential FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Beauty to electrons Expected ALICE performance (1 month Pb-Pb) e± identification from TRD and dE/dx in TPC impact parameter from ITS S/(S+B) S per 107 central Pb-Pb events FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Electrons (from b) pt spectrum stat  syst error Error composition stat error 11% from overall normalization not included FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Beauty to single muons expected in the muon arm  very high statistics and heavy flavour purity expected FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Beauty to dimuons Two main sources: B µ+ + D + X µ- + X B µ- + X “BDSAME” “BBDIFF” FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Beauty to dimuons Consistency check! low mass mm high mass mm low mass: µ+ and µ- from decay of same B or B high mass: µ+ and µ- from decay of B and B FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Expected ALICE performance on D, B RAA mass dependence colour charge dependence mb = 4.8 GeV D0  K-p+ B  e + X 1 year at nominal luminosity (107 central Pb-Pb events, 109 pp events) FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Charm v2 at LHC? Full reconstruction of D decays at LHC qualitatively different measurement from non-photonic electrons! b vs c better correlation with original heavy-quark momentum First indications from preliminary studies in ALICE: expected error ~ few % (D v2) FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Ds+ Ds+ as probe of hadronization? from string fragmentation: cs / cd ~ 1/3 after decays: Ds+ (cs) / D+ (cd) ~ 0.6 from recombination: cs / cd ~ N(s) / N(d)  how large at LHC? experimentally accessible? D+ (ct ~ 310 µm)  K-p+p+ with BR ~ 9.2 % in Alice: similar performance as for D0  K-p+ Ds+ (ct ~ 150 µm)  K-K+p+ with BR ~ 4.4 % but mostly resonant decays: Fp+ or K0*K+ (non resonant only 20 %)  favours bkgnd rejection (for D+  K-p+p+, non-resonant ~ 96 %) may be well visible (expecially if Ds+/D+ is large!) Ds v2 would be particularly interesting! FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

At LHC: real jets! 2 GeV 20 GeV 100 GeV 200 GeV Mini-Jets 100/event 1/event 100k/month Well visible event-by-event! e.g. 100 GeV jet + underlying event: e.g.: study quenching with b-tagged jets!

b tagging ATLAS u rejection (Ru) performance in Pb-Pb H  bb, uu with MH = 400 GeV FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Away side cone? Collective behaviour opposite to jet? PHENIX Preliminary Dq*=p Df*=0 Collective behaviour opposite to jet? eg: Mach cone John Lajoie @ QM2006 [Casalderrey-Solana, et al.: hep-ph/0411315] [Stocker: Nucl.Phys. A750 (2005) 121]) Assume effect is real: What happens with big-fat-heavy quark jets? FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Modified Mach cone? Heavy quarks at moderate pT move with substantially lower speed e.g.: for beauty, taking: cS2 = 0.2 m(b) = 4.5 GeV b quark is “subsonic” for p < 2.25 GeV for p ~ 3-4 GeV, shock wave angle ~ 40O [FA, E Shuryak: J.Phys. G31 (2005) 19] shock wave angle [degrees] Now: observing THAT would be something! p(b) [GeV] FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

Conclusioni Con gli heavy flavour, la Natura ci mette gentilmente a disposizione un meraviglioso strumento per studiare le proprietà del mezzo prodotto nelle collisioni nucleari ultrarelativistiche LHC è una macchina da heavy flavour alte rese di produzione molto gamma in pT estesa jet ben sviluppati L’esperimento ALICE è ben attrezzato per questa fisica FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009