Presentation is loading. Please wait.

Presentation is loading. Please wait.

1 Introduzione alla fisica degli heavy flavour nelle collisioni nucleari ultrarelativistiche Federico Antinori (INFN, Padova & CERN, Ginevra) FA - Quark.

Similar presentations


Presentation on theme: "1 Introduzione alla fisica degli heavy flavour nelle collisioni nucleari ultrarelativistiche Federico Antinori (INFN, Padova & CERN, Ginevra) FA - Quark."— Presentation transcript:

1 1 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

2 2 LHC is a Heavy Flavour Machine! cc and bb rates cc and bb rates ALICE PPR (NTLO + shadowing) ALICE PPR (NTLO + shadowing) 115 / / / 0.2 Pb-Pb 5.5 TeV (5% cent) 0.16 / / / 0.5 pp 14 TeV shadowingsystem NN x-sect (mb) total multiplicity PbPb pp PbPb pp cc bb PbPb/pp

3 3 Probing the medium with heavy flavours c, b produced in early stages of collision, then conserved (neglecting annihilation) 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 ideal probes of bulk, strongly interacting phase energy loss? energy loss? thermal production? thermal production? no extra production at hadronization no extra production at hadronization ideal probes of fragmentation ideal probes of fragmentation independent string fragmentation vs recombination independent string fragmentation vs recombination FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

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

5 Parte prima : introduzione, heavy flavour in collisioni elementari 5 FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

6 6 Heavy Flavour Decays FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

7 7 Some zoology... Lower mass heavy flavour hadrons decay weakly Lower mass heavy flavour hadrons decay weakly ~ ps ~ ps c ~ 100s µm c ~ 100s µm weakly decaying states from PDG 2006 summary tables: weakly decaying states from PDG 2006 summary tables: FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

8 8 Impact parameter ~ c Impact parameter ~ c In UR limit b ~ Lorentz invariant: In UR limit b ~ Lorentz invariant:... so b ~ independent of... so b ~ independent of if cos CM distribution is flat: if cos CM distribution is flat: so, in space, in projection: in projection:so: primary vertex decay vertex decay length = L impact parameter = b yx d b FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

9 9 Weak decays of charm typically: typically: large branching ratio to kaons: large branching ratio to kaons: D + : D + : D + K - +X BR ~ 28 % D + K - +X BR ~ 28 % golden channel: D + K BR ~ 9% golden channel: D + K BR ~ 9% D 0 : D 0 : D 0 K - +X BR ~ 50% D 0 K - +X BR ~ 50% golden channels: D 0 K - + BR ~ 4% ; D 0 K BR ~ 7% golden channels: D 0 K - + BR ~ 4% ; D 0 K BR ~ 7% W ± branchings: W ± branchings: large semileptonic branching ratio, varies with heavy flavour particle, typical ~ 10% 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 p T...) cs W+W+W+W+ cs W+W+W+W+ u d e+e+e+e+ e µ+µ+µ+µ+ µ bc W-W-W-W- (similarly: ) C = Cabibbo angle C = Cabibbo angle FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

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

11 11 Heavy Flavour Production in QCD FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

12 12 Heavy Flavour hadro-production in pQCD Factorization: Factorization: hadron hadroncharmedhadron cross-section at parton level e.g.: parton distribution functions x a = momentum fraction of parton a in hadron A fragmentation z = fraction of c momentum to hadron D cross-section at hadron level a=q b=q Q Q (at sufficiently large Q 2 ) FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

13 13 factorization implies: factorization implies: PDFs can be measured with one reaction... PDFs can be measured with one reaction... say: Drell-Yan: A+B e + e - + X say: Drell-Yan: A+B e + e - + X... and used to calculate a different one say: heavy-flavour production say: heavy-flavour production fragmentation independent of the reaction (e.g.: same in pp, e + e - ) fragmentation independent of the reaction (e.g.: same in pp, e + e - ) FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

14 14 Parton Distribution Functions PDFs vary depending on momentum transfer scale Q 2 PDFs vary depending on momentum transfer scale Q 2 Intuitively: Intuitively: higher Q 2 -> higher resolution high-x parton -> lower-x partons The Q 2 evolution of the PDFs can be calculated in pQCD The Q 2 evolution of the PDFs can be calculated in pQCD Altarelli-Parisi evolution Altarelli-Parisi evolution(DGLAP) FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

15 15 Leading-order (LO) Relevant diagrams: pair creation Relevant diagrams: pair creation qq QQ (quark-antiquark annihilation) qq QQ (quark-antiquark annihilation) gg QQ (gluon-gluon fusion) gg QQ (gluon-gluon fusion) q q Q Q Q Q g g Q Q g g Q Q g g FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

16 16 A few results the partonic cross-section decreases with energy the partonic cross-section decreases with energy faster for qq than for gg (which therefore is expected to dominate, except near threshold) faster for qq than for gg (which therefore is expected to dominate, except near threshold) the parton luminosities near threshold increase with energy, 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: the pair cross section is proportional to: y (y): rapidity of Q (Q) Q and Q therefore expected to be close in y Q and Q therefore expected to be close in y Experimentally: EHS, 360 GeV - p DDX Experimentally: EHS, 360 GeV - p DDX [EHS: PLB 123 (1983) 98] FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

17 17 Next-To-Leading-Order (NTLO) in absolute value, LO cross sections are typically underestimated by factor (K factor) in absolute value, LO cross sections are typically underestimated by factor (K factor) at NTLO: additional diagrams, such as: at NTLO: additional diagrams, such as: Q Q Q Q Q Q higher order corrections to pair creation flavour excitation gluon splitting FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

18 18 the agreement with experiment for the total cross-section is good (within large bands...) the agreement with experiment for the total cross-section is good (within large bands...) e.g.: charm cross section at fixed target: e.g.: charm cross section at fixed target: [Mangano: hep-ph/ ] FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

19 19 results depend on the values of: results depend on the values of: m c, µ R (renormalization scale), µ F (factorization scale) m c, µ R (renormalization scale), µ F (factorization scale) the result of an exact calculation would be independent of the choice of the scale parameters µ R, µ F the result of an exact calculation would be independent of the choice of the scale parameters µ R, µ F the residual scale dependence is a measure of the accuracy of the calculation the residual scale dependence is a measure of the accuracy of the calculation e.g.: for b production at Tevatron (µ R =µ F =µ): e.g.: for b production at Tevatron (µ R =µ F =µ): [Mangano: hep-ph/ ] FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

20 20 it is important to match the PDFs with the order of the calculation. it is important to match the PDFs with the order of the calculation. e.g. one must avoid double counting: e.g. one must avoid double counting: at LO: at LO: at NTLO: at NTLO: intrinsic flavour flavour excitation Q Q QQ FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

21 21 Heavy Flavour in p/ -A FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

22 22 Nuclear shadowing PDFs in the nucleus different from PDFs in free proton PDFs in the nucleus different from PDFs in free proton R = ratio of nuclear to nucleon PDFs R = ratio of nuclear to nucleon PDFs from Deep Inelastic Scattering (e - +p; e - +A), Drell-Yan (p+p, p+A -> l + l - +X) 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] typical x for cc production (y 0) typical x for cc production (y 0) x 10 SPS x 10 SPS x 10 RHIC x 10 RHIC x a few 10 LHC x a few 10 LHC shadowing antishadowing SPS RHIC LHC FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

23 23 Nuclear dependence From pQCD one expects the cross section for production off nuclei to increase like number of nucleon-nucleon collisions 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): proportional to number of nucleons (for min. bias collisions): modulo shadowing effects, expected to be small modulo shadowing effects, expected to be small Experimentally: not far... e.g. WA82: Experimentally: not far... e.g. WA82: D production in - +W/Si at SPS (340 GeV beam momentum) D production in - +W/Si at SPS (340 GeV beam momentum) (relatively) central production (relatively) central production with =1 Feynmans x FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

24 24Caveats... i) = 1 does not work down to pp! i) = 1 does not work down to pp! e.g.: MacDermott & Reucroft compare pA results with earlier hydrogen data from NA27, good agreement using: 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! 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, K, p from p on nuclear targets: with FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

25 25 ii) lower at large x F ? ii) lower at large x F ? early beam dump experiments, sensitive at large x F (max acceptance for x F 0.5) early beam dump experiments, sensitive at large x F (max acceptance for x F 0.5) (in tracking experiments, typically max. acceptance for x F 0.2) e.g. WA78 [Cobbaert et al.: PLB 191 (1987) 456] for muons escaping dump ( - A at 320 GeV FT ): for muons escaping dump ( - A at 320 GeV FT ): note: is known to decrease note: is known to decrease with x F for light hadrons [Barton et al.: PRD 27 (1983) 2580] FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

26 26 Heavy Flavour Fragmentation FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

27 27Fragmentation String fragmentation model: String fragmentation model: (e.g. [PYTHIA (e.g. [PYTHIA hep-ph/ ]) as coloured quarks fly away, energy is stored in the field: 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 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 string snaps, e.g.: the heavy quark ends up hadronising together with a light antiquark the newly created quarks are of course light the newly created quarks are of course light estimated ratios: estimated ratios: u : d : s : c 1 : 1 : 0.3 : no heavy flavour production in string breaking! no heavy flavour production in string breaking! 1 GeV/fm FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

28 28 Fragmentation function c D, D takes fraction z of c momentum c D, D takes fraction z of c momentum fragmentation function: D D/c (z) fragmentation function: D D/c (z) depends only on fraction z depends only on fraction z e.g.: e.g.: Peterson Colangelo-Nason Peterson ( = 0.015) Colangelo-Nason ( = 0.9, =6.4) e.g.: (parameters from fits to charm production at LEP) FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

29 29 How to measure the fragmentation function? How to measure the fragmentation function? we dont measure the original Q momentum... we dont measure the original Q momentum... but in e + e - we do know the Q momentum (by energy conservation!) but in e + e - we do know the Q momentum (by energy conservation!) e.g.: e.g.: fragmentation functions are usually extracted from e + e - measurements and then used for other collisions fragmentation functions are usually extracted from e + e - measurements and then used for other collisions e-e- Q Q e+e+ Z0Z0 FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

30 30 e.g.: fits to charm x = 2E/ s distributions in e + e - : 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) very similar parameters at the two energies (as expected) s = 10.6 GeV (ARGUS) s = 91.2 GeV (OPAL) Peterson fragmentation = (OPAL) = (ARGUS) FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

31 31 like for the PDFs, the fragmentation function has to be matched to order of pQCD calculation like for the PDFs, the fragmentation function has to be matched to order of pQCD calculation e.g. at NTLO a Q can radiate: e.g. at NTLO a Q can radiate: so final energy before so final energy before non-perturbative part of fragmentation lower than at LO harder fragmentation at NTLO harder fragmentation at NTLO at NTLO: at NTLO: at LO: 0.06 at LO: 0.06 (e.g.: [Cacciari & Greco: PRD55 (1997) 7134] ) Peterson fragmentation = (NTLO) = 0.06 (LO) Q Q FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

32 32 D* decays, D 0 (cu) / D + (cd) ratio FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

33 33 D* decays Most of the D mesons (from spin counting, ~ 75%) are not directly produced at hadronization, but in D* decays Most of the D mesons (from spin counting, ~ 75%) are not directly produced at hadronization, but in D* decays D ±, D 0 J=0 D ±, D 0 J=0 D *±, D *0 J=1 D *±, D *0 J=1 Due to fine tuning of the values of the masses: Due to fine tuning of the values of the masses: m(D ± ) + m( 0 ) < m(D *± ) m(D ± ) + m( 0 ) < m(D *± ) m(D 0 ) + m( ± ) < m(D *± ) m(D 0 ) + m( ± ) < m(D *± ) m(D 0 ) + m( 0 ) < m(D *0 ) m(D 0 ) + m( 0 ) < m(D *0 )but... m(D ± ) + m( ± ) > m(D *0 ) m(D ± ) + m( ± ) > m(D *0 )... the light quark content of charged D is preserved also in case of resonance decays:... the light quark content of charged D is preserved also in case of resonance decays: a D 0 (cu) can originate from either D *0 (cu) or D *+ (cd) a D 0 (cu) can originate from either D *0 (cu) or D *+ (cd) a D + (cd) can only originate from a D *+ (cd) a D + (cd) can only originate from a D *+ (cd) FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

34 34 D 0 /D + ratio at LEP D *0 and D *+ both decay strongly into Ds, but: D *0 and D *+ both decay strongly into Ds, but: D *+ can decay to both D 0 and D + D *+ can decay to both D 0 and D + D *0 can only decay to D 0 D *0 can only decay to D 0 From spin degeneracy one expects: From spin degeneracy one expects: D 0 : D + : D *0 : D *+ = 1 : 1 : 3 : 3... and therefore a large D 0 /D + ratio... and therefore a large D 0 /D + ratio using the experimental branching ratios: using the experimental branching ratios: but experimentally, at LEP: but experimentally, at LEP: [ALEPH: EPJ C16 (2000) 597] FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

35 35 Heavy Flavour at Tevatron FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

36 36 Beauty at Tevatron Discrepancy between pQCD and data seems to have disappeared... Discrepancy between pQCD and data seems to have disappeared... from... from... a factor 5.5 (but only ) to... to... [CDF: PRL 68 (1992) 3403] Run 0 Run II [Cacciari et al: JHEP 0407 (2004)] Spectrum of J/ from secondary B decays FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

37 37 From run I on, important improvements in accuracy: From run I on, important improvements in accuracy: experiment (vertex detectors, high statistics) experiment (vertex detectors, high statistics) prediction (post-HERA PDF sets) prediction (post-HERA PDF sets) Levels of stability over time: Levels of stability over time: no large room for new physics any more... no large room for new physics any more... for more see, e.g.: for more see, e.g.: [Cacciari et al: JHEP 0407 (2004) 033, Cacciari: hep-ph/ , Mangano: hep-ph/ ] DataPredictions from [Cacciari et al: JHEP 0407 (2004) 033] FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

38 38 What about charm? Nice data from CDF run II Nice data from CDF run II [CDF: Phys.Rev.Lett. 91 (2003) ] roughly in agreement with full pQCD calculation roughly in agreement with full pQCD calculation (though prediction somewhat low) A curiosity (?): 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

39 Parte seconda : heavy flavour in collisioni nucleo-nucleo 39 FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

40 40 Charm and beauty: ideal probes study medium with probes of known colour charge and mass study medium with probes of known colour charge and mass e.g.: energy loss by gluon radiation expected to be: e.g.: energy loss by gluon radiation expected to be: parton-specific: stronger for gluons than quarks (colour charge) parton-specific: stronger for gluons than quarks (colour charge) flavour-specific: stronger for lighter than for heavier quarks (dead-cone effect) 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) study effect of medium on fragmentation (no extra production of c, b at hadronization) independent string fragmentation vs recombination independent string fragmentation vs recombination e.g.: D + s /D + e.g.: D + s /D + + measurement important for quarkonium physics + measurement important for quarkonium physics open QQ production natural normalization for quarkonium studies open QQ production natural normalization for quarkonium studies B meson decays non negligible source of non-prompt J/ B meson decays non negligible source of non-prompt J/ FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

41 41 Heavy flavour production in AA binary scaling: binary scaling: can be broken by: initial state effects (modified PDFs) initial state effects (modified PDFs) shadowing shadowing k T broadening k T broadening gluon saturation (colour glass) gluon saturation (colour glass) (concentrated at lower p T ) final state effects (modified fragmentation) final state effects (modified fragmentation) parton energy loss parton energy loss violations of independent fragmentation (e.g. quark recombination) violations of independent fragmentation (e.g. quark recombination) (at higher p T ) FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

42 42 What do we know from the SPS? Intermediate mass dimuon excess in central Pb-Pb at SPS (NA50) Intermediate mass dimuon excess in central Pb-Pb at SPS (NA50) Main known sources in that region: Drell-Yan and charm pairs Main known sources in that region: Drell-Yan and charm pairs M (GeV/c 2 ) central collisions FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

43 43 Study of the I.M. excess in NA60 Fit weighted impact parameter distribution Fit weighted impact parameter distribution prompt from J/ ψ dimuons, charm from PYTHIA prompt from J/ ψ dimuons, charm from PYTHIA requires > 2 x expected D-Y to fit data requires > 2 x expected D-Y to fit data 6500 A, 2 match < 3 sensitivity to assumption on cc p T, Δφ sensitivity to assumption on cc p T, Δφ extracted value of cc cross section ~ 2 – 3 larger than extrap. extracted value of cc cross section ~ 2 – 3 larger than extrap. but compatible with extrapolation from NA50 p-A but compatible with extrapolation from NA50 p-A NA60 H.Woehri and C.Lourenco, Phys.Rep. 433 (2006) FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

44 44 Heavy RHIC: experimental techniques FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

45 45 Non-photonic electrons Identified electron spectra Identified electron spectra STAR: dE/dx in TPC + TOF at low p T, EMC at high p T STAR: dE/dx in TPC + TOF at low p T, EMC at high p T PHENIX: combined RICH and E/p (with E from EM cal) PHENIX: combined RICH and E/p (with E from EM cal) Rejection of non-heavy-flavour electrons Rejection of non-heavy-flavour electrons Main source of electrons: photonic Main source of electrons: photonic e + e - conversions e + e - conversions Dalitz decays 0 e + e - Dalitz decays 0 e + e - Dalitz decays e + e - Dalitz decays e + e - STAR: STAR: rejected by full invariant mass analysis of e + e - combinations rejected by full invariant mass analysis of e + e - combinations PHENIX: PHENIX: estimated by simulation and subtracted (cocktail method) estimated by simulation and subtracted (cocktail method) measured by converter method and subtracted measured by converter method and subtracted Other sources of non-charm electrons: Other sources of non-charm electrons:,,, K decays,,, K decays estimated by sim. and subtracted (in both STAR and PHENIX) estimated by sim. and subtracted (in both STAR and PHENIX) (internal conversions) FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

46 46 Reconstructed decays (STAR) D 0 K D 0 K tracks from TPC tracks from TPC K, identification from dE/dx K, identification from dE/dx no separation of D decay vertex no separation of D decay vertex large combinatiorial background evaluated by event mixing and subtracted large combinatiorial background evaluated by event mixing and subtracted residual background, subtracted with linear fit residual background, subtracted with linear fit FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

47 47 Low p T muons (STAR) in TPC (dE/dx) in TPC (dE/dx) in TOF in TOF 3. fit to impact parameter distribution charm should ~ point to primary... charm should ~ point to primary... [C Zhang (STAR) QM06] FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

48 48 Experimental status FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

49 49 PHENIX pp Excess wrt FONLL: Excess wrt FONLL: Similar situation also in CDF: Similar situation also in CDF: [A. Adare et al. (PHENIX) Phys.Rev.Lett. 97 (2006) ] Ratio: (stat) 0.19 (sys) (0.3 < p T < 9.0 GeV/c) D0D0 [D. Acosta et al. (CDF) PRL 91 (2003) ] FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

50 50 STAR v PHENIX pp ~ a factor 2 discrepancy ~ a factor 2 discrepancy hep-ex/ [J. Lajoie (PHENIX) QM06] FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

51 51 STAR dAu, AuAu Internal consistency Internal consistency [M. Calderon (STAR) QM06] FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

52 52 STAR v PHENIX dAu, AuAu Discrepancy pretty stable v collision system, channel, p T Discrepancy pretty stable v collision system, channel, p T looks like something very basic... looks like something very basic... of course then R AA not too different... of course then R AA not too different... [A. Suaide QM06] FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

53 53 STAR v PHENIX: R AA R AA of non-photonic electrons R AA of non-photonic electrons [A. Suaide QM06] similar picture from STAR and PHENIX similar picture from STAR and PHENIX FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

54 54 Interpretations FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

55 55Theoretically... 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 light hadrons originate from a mixture of gluon and quark jets, heavy flavoured hadrons originate from quark jets C R is 4/3 for quarks, 3 for gluons C R is 4/3 for quarks, 3 for gluons ii)dead-cone effect gluon radiation expected to be suppressed for < M Q /E Q gluon radiation expected to be suppressed for < M Q /E Q [Dokshitzer & Karzeev, Phys. Lett. B519 (2001) 199] [Armesto et al., Phys. Rev. D69 (2004) ] Casimir coupling factor transport coefficient of the medium average energy loss distance travelled in the medium R.Baier et al., Nucl. Phys. B483 (1997) 291 (BDMPS) FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

56 56Experimentally... non ph. el. ~ as suppressed as light hadrons non ph. el. ~ as suppressed as light hadrons use of high density (qhat), introduction of elastic (in addition to radiative) energy loss... not enough use of high density (qhat), introduction of elastic (in addition to radiative) energy loss... not enough high qhat and no beauty electrons does better high qhat and no beauty electrons does better [B.I. Abelev et al (STAR): nucl-ex/ ] FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

57 57 How much beauty? high p T region expected to be beauty-dominated high p T region expected to be beauty-dominated but how high? but how high? [M. Cacciari et al.: PRL 95 (2005) ] not easy to disentangle c/b contributions to RHIC non ph. el. samples (no heavy flavour vertex detectors in RHIC experiments) not easy to disentangle c/b contributions to RHIC non ph. el. samples (no heavy flavour vertex detectors in RHIC experiments) [A. Suaide QM06] FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

58 58 E loss being understood? DongJo Kim (PHENIX) FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

59 59 another sobering caveat… Relative abundances in charm sector also important: Relative abundances in charm sector also important: c /D (e c )/(e D) D0D0D0D0D Ds+Ds+Ds+Ds+ c + c + BR (X e) in % Sebastien Gadrat (see also P Sorensen & X Dong, PRC 74 (2006) ) and what about D s ? and what about D s ? s enhancement! s enhancement! e.g.: Λ c /D may change from pp to AA e.g.: Λ c /D may change from pp to AA FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

60 60 Vertex Detectors! need less indirect measurement need less indirect measurement full reconstruction of charm decays! full reconstruction of charm decays! get rid of b/c ambiguities get rid of b/c ambiguities study relative abundances in charm sector study relative abundances in charm sector Silicon Pixels in ALICE (+ ATLAS, CMS) Silicon Pixels in ALICE (+ ATLAS, CMS) Silicon Vertex upgrades in STAR, PHENIX Silicon Vertex upgrades in STAR, PHENIX FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

61 61 Track Impact Parameter track impact parameter (d 0 ): separation of secondary tracks from HF decays from primary vtx track impact parameter (d 0 ): separation of secondary tracks from HF decays from primary vtx FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

62 62 PIXEL CELL z: 425 m r : 50 m Two layers: r = 4 cm r = 7 cm 9.8 M e.g.: D 0 K - + Impact parameter measurement in ALICE expected d 0 resolution ( ) expected d 0 resolution ( ) ALICE Silicon Pixels ALICE Silicon Pixels FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

63 63 LHC is a Heavy Flavour Machine! cc and bb rates cc and bb rates ALICE PPR (NTLO + shadowing) ALICE PPR (NTLO + shadowing) 115 / / / 0.2 Pb-Pb 5.5 TeV (5% cent) 0.16 / / / 0.5 pp 14 TeV shadowingsystem NN x-sect (mb) total multiplicity PbPb pp PbPb pp cc bb PbPb/pp FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

64 64 large cross-sections large cross-sections low-x (a field on its own!) low-x (a field on its own!) accessible x1, x2 regions in the ALICE experiment accessible x1, x2 regions in the ALICE experiment central detector muon arm FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

65 65 Heavy Flavour Quenching? some prediction... some prediction... [Armesto et al.: Phys.Rev. D71 (2005) ] charm beauty FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

66 66 D 0 K - + expected ALICE performance expected ALICE performance S/B 10 % S/B 10 % S/ (S+B) 40 (1 month Pb-Pb running) S/ (S+B) 40 (1 month Pb-Pb running) statistical. systematic. p T - differential similar performance in pp similar performance in pp (wider primary vertex spread) (wider primary vertex spread) FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

67 67 Beauty to electrons Expected ALICE performance (1 month Pb-Pb) Expected ALICE performance (1 month Pb-Pb) e ± identification from TRD and dE/dx in TPC e ± identification from TRD and dE/dx in TPC impact parameter from ITS impact parameter from ITS S/(S+B) S per 10 7 central Pb-Pb events FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

68 68 Electrons (from b) p t spectrum Error composition stat error stat syst error 11% from overall normalization not included FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

69 69 Beauty to single muons expected in the muon arm expected in the muon arm very high statistics and heavy flavour purity expected very high statistics and heavy flavour purity expected FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

70 70 Beauty to dimuons Two main sources: Two main sources: Bµ + + D + X µ - + X B B X + µ + BD SAME BB DIFF FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

71 Beauty to dimuons 71 low mass high mass low mass: µ+ and µ- from decay of same B or B high mass: µ+ and µ- from decay of B and B Consistency check! Consistency check! FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

72 72 Expected ALICE performance on D, B R AA m b = 4.8 GeV D 0 K B e + X 1 year at nominal luminosity (10 7 central Pb-Pb events, 10 9 pp events) mass dependence colour charge dependence FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

73 73 Charm v 2 at LHC? Full reconstruction of D decays at LHC Full reconstruction of D decays at LHC qualitatively different measurement from non-photonic electrons! qualitatively different measurement from non-photonic electrons! b vs c b vs c better correlation with original heavy-quark momentum better correlation with original heavy-quark momentum First indications from preliminary studies in ALICE: expected error ~ few % (D v 2 ) First indications from preliminary studies in ALICE: expected error ~ few % (D v 2 ) FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

74 74 Ds+Ds+Ds+Ds+ D s + as probe of hadronization? D s + as probe of hadronization? from string fragmentation: cs / cd ~ 1/3 from string fragmentation: cs / cd ~ 1/3 after decays: D s + (cs) / D + (cd) ~ 0.6 after decays: D s + (cs) / D + (cd) ~ 0.6 from recombination: cs / cd ~ N(s) / N(d) from recombination: cs / cd ~ N(s) / N(d) how large at LHC? how large at LHC? experimentally accessible? experimentally accessible? D + (c ~ 310 µm) K with BR ~ 9.2 % D + (c ~ 310 µm) K with BR ~ 9.2 % in Alice: similar performance as for D 0 K - + in Alice: similar performance as for D 0 K - + D s + (c ~ 150 µm) K - K + + with BR ~ 4.4 % D s + (c ~ 150 µm) K - K + + with BR ~ 4.4 % but mostly resonant decays: + or K 0 * K + (non resonant only 20 %) but mostly resonant decays: + or K 0 * K + (non resonant only 20 %) favours bkgnd rejection (for D + K - + +, non-resonant ~ 96 %) favours bkgnd rejection (for D + K - + +, non-resonant ~ 96 %) may be well visible (expecially if D s + /D + is large!) may be well visible (expecially if D s + /D + is large!) D s v 2 would be particularly interesting! D s v 2 would be particularly interesting! FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

75 75 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: Well visible event-by-event! e.g. 100 GeV jet + underlying event: e.g.: study quenching with b-tagged jets! e.g.: study quenching with b-tagged jets!

76 76 b tagging ATLAS u rejection (R u ) performance in Pb-Pb ATLAS u rejection (R u ) performance in Pb-Pb H bb, uu with M H = 400 GeV H bb, uu with M H = 400 GeV FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

77 77 Away side cone? Collective behaviour opposite to jet? Collective behaviour opposite to jet? eg: Mach cone eg: Mach cone [Casalderrey-Solana, et al.: hep-ph/ ] [Stocker: Nucl.Phys. A750 (2005) 121]) Assume effect is real: What happens with big-fat-heavy quark jets? What happens with big-fat-heavy quark jets? PHENIX Preliminary *= John QM2006 FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

78 78 Modified Mach cone? Heavy quarks at moderate p T move with substantially lower speed Heavy quarks at moderate p T move with substantially lower speed e.g.: for beauty, taking: e.g.: for beauty, taking: c S 2 = 0.2 c S 2 = 0.2 m(b) = 4.5 GeV m(b) = 4.5 GeV b quark is subsonic b quark is subsonic for p < 2.25 GeV for p ~ 3-4 GeV, for p ~ 3-4 GeV, shock wave angle ~ 40 O [FA, E Shuryak: J.Phys. G31 (2005) 19] p(b) [GeV] shock wave angle [degrees] Now: observing THAT would be something! FA - Quark Matter Italia - Roma Sanità - 24 aprile 2009

79 79Conclusioni 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 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 LHC è una macchina da heavy flavour alte rese di produzione molto alte rese di produzione molto gamma in p T estesa gamma in p T estesa jet ben sviluppati jet ben sviluppati Lesperimento ALICE è ben attrezzato per questa fisic a Lesperimento ALICE è ben attrezzato per questa fisic a


Download ppt "1 Introduzione alla fisica degli heavy flavour nelle collisioni nucleari ultrarelativistiche Federico Antinori (INFN, Padova & CERN, Ginevra) FA - Quark."

Similar presentations


Ads by Google