Op en Charm Ph ysics at SPS and RHIC Ziw ei Lin T exas - PDF document

Op en Charm Ph ysics at SPS and RHIC Ziw ei Lin T exas A&M Univ ersit y Pro duction in pp Leading-Order Pro cesses Higher-Order Results F ragmen tation F unctions T otal Cross Section vs Data Pro duction in AA Scaling Observ ables at RHIC High- p Suppression from Energy loss ? Mid- p Enhancemen t from Radial Flo w at SPS ? ? from Radial Flo w at RHIC Op en Charm in pA at RHIC Summary R WW'99, 1/9/99

Wh y do w e need op en c harm? J = suppression suppression of total c harm or only J = Thermal dileptons needs go o d understanding of con tin uum dilepton sp ectra Thermalization sensitiv e to energy loss and thermalization e�ects R WW'99, 1/9/99

pp Op en Charm Pro duction in c _ c Leading Order Diagrams Gluon Quark X2 c - c X1 Com bridge, NPB151,429(79) Scale set b y m 1 : 3 GeV ' c P erturbativ e QCD w orks reasonably w ell: d� d � ^ Z dx f ( x ) dx f ( x ) / 1 1 2 2 ^ 3 d p d t R WW'99, 1/9/99

NLO c harm pro duction: 3 Hea vy quark pro duction at O ( � ): Nason et al, NPB303,607(88); 327,49(89) Beenakk er et al, PRD40,54(89); NPB351,507(91) see Nason hep-ph/9811468 for more LO + N LO K-factor � LO Almost constan t o v er the whole phase space! K far from 1: imp ortance of higher order terms. V ogt, ZPC71,475(96) R WW'99, 1/9/99

Charm F ragmen tation in Hadropro ductions + � a e e data suggests the P eterson form : 1 D ( z ) / 2 z [1 � 1 =z � �= (1 � z )] E769, consisten t with EITHER: bare c harm quark sp ectra 2 2 OR :P eterson plus in trinsic < k > of 2 GeV ? E706, higher p co v erage, ? 2 2 consisten t with P eterson plus in trinsic < k > of 1 2 GeV � ? -1 nucleon)) π - N → D ± X at 515 GeV/c 10 Data d σ /dp T ( µ b/(GeV c NLO QCD Charm quarks NLO QCD + Frag. + < k T 2 > =3.0 (GeV/c) 2 1 NLO QCD + Frag. + < k T 2 > =2.0 (GeV/c) 2 NLO QCD + Frag. + < k T 2 > =1.0 (GeV/c) 2 NLO QCD + Frag. + < k T 2 > =0.0 (GeV/c) 2 10 -1 10 -2 10 -3 10 -4 x F > -0.2 10 -5 0 1 2 3 4 5 6 7 8 p T (GeV/c) a 2 z � p =p , � = 0 : 06(LO), 0 : 02 (NLO); � / 1 =m c D Q R WW'99, 1/9/99

� a D D correlation in hadropro ductions : High- p direct photon and � data suggests: ? 2 2 2 < k > ' 1 GeV +C Q ? Op en c harm hadropro duction most consisten t ) with P eterson fragmen tation+parton in trinsic k ? a W A92, PLB385,487(96) R WW'99, 1/9/99

T otal Cross Section vs Data F rom leading-order calculation: _ σ (pp−>cc X) ( µ b) Lin, Phys Rev C 100 E653 NA34 NA27 E743 E789 10 MRSA, mc=1.3GeV, K=2.5 MRSA, mc=1.4GeV, K=2.5 GRV−HO, mc=1.3GeV, K=3 1 100 200 300 400 500 600 700 800 900 1000 P lab (GeV) Large uncertain t y from scale and quark mass. Ho w ev er, data helps to constrain parameters, NLO & resummation help, making ratios helps(systematic studies) R WW'99, 1/9/99

AA Op en Charm Pro duction in Scaling from pp to AA ( shadowing on n uclear structure function will b e discussed later) c � c d� AB c c � T ( b ) � / � AB pp 2 d b Open Charm production up to RHIC energy 1000 100 pp → c c _ µ b 10 MRSA, 1.3GeV, K=2.5 MRSA, mc=1.4GeV, K=2.5 1 GRV−HO, mc=1.3GeV, K=3 0 0 NA50 50 100 150 200 RHIC sqrt(s) (GeV) c c � � 350 �b (at 200GeV), T (0) 30 =mb ' ' AA pp large op en c harm pro duction at RHIC! ) F or an a v erage cen tral Au + Au ev en t: ~ c � c c c � N ( b = 0) = T (0) � 10 � ' AA pp R WW'99, 1/9/99

Small secondary c harm pro duction Pre-equilibrium charm production from minijets Minijets c additional charm production _ c 0 10 1 Initial fusion -1 Au+Au(b=0) strong η −y correlation 10 −1 10 1/2 =200 GeV dN/dyd 2 p T (y=0) (GeV -2 c 2 ) s Bjorken correlation -2 Ed 3 N/d 3 p(Y=0) (GeV −2 ) 10 fireball case −2 -3 10 10 -4 10 −3 10 -5 10 −4 -6 10 10 initial fusion -7 10 −5 pre-thermal 10 thermal -8 10 ideal thermal −6 -9 10 10 0.0 2.0 4.0 6.0 8.0 10.0 0 1 2 3 4 5 6 7 8 p T (GeV/c) charm P T (GeV) Fig. 5 Lin & Gyulassy ,PR C51,2177(95) L � ev ai,M � uller&W ang,PR C51,3326(95) R WW'99, 1/9/99

Observ ables from op en c harm: D-mesons: � D K � � ! � � � leptons: � D e , D � ! � � � ! � � � � dileptons from D/ D pairs: � � + � D e , D e ! � � � ! � � � ) + + + + lik e-sign pairs: e e ; e � ; { � � � + + � � opp osite-sign pairs: e e ; e � ; { � � � � correlated pairs: from one D/ D pair � � uncorrelated pairs: from t w o D/ D pairs � R WW'99, 1/9/99

RHIC ST AR? PHENIX? PHENIX, go o d PHENIX,go o d R WW'99, 1/9/99

Large Dilepton Yield from Charm Deca ys Larger than Drell-Y an, PHENIX is able to see those: from Akiba R WW'99, 1/9/99

Hea vy quark ma y ha v e energy loss charm quark p t spectrum Sh ury ak, PR C55,961(97); Lin, V ogt & W ang, PR C57,899(98) 9.94E6 ccbar events 2 10 before energy loss after energy loss 1 10 thermalized part −1 ) dN/dp t (GeV 0 10 −1 10 −2 10 −3 10 0 2 4 6 8 10 D−meson p t (GeV) Suppressions of high- p D mesons, as w ell as high- p � ? ? leptons and high- M dileptons from c harm deca ys. a No evidence of jet quenc hing for pions A t SPS � large formation time for fast pions? ! hea vy quarks migh t b e the b est prob e of energy loss � Figure: assumed dE/dx=-1GeV/fm, Lin, V ogt & W ang, PR C57 a W ang, PRL81,2655(98) R WW'99, 1/9/99

PHENIX will then see a large suppression: E > 1 GeV, � 2 ( � 0 : 35 ; 0 : 35); E > 2 GeV, j � j 2 (1 : 15 ; 2 : 44) e e � � + µ − Spectra from Open Charm at PHENIX + e − Spectra from Open Charm at PHENIX e µ Spectra from Open Charm at PHENIX µ e flow: de/dx=−2GeV/fm, T=150MeV flow: de/dx=−2GeV/fm, T=150MeV flow: de/dx=−2GeV/fm, T=150MeV −3 −3 10 10 + µ − e µ µ + e − e −4 −4 10 10 −5 −5 10 10 −1 ) − (GeV −6 −6 10 10 l + dN/dM l −7 −7 10 10 original charm suppressed charm original bottom −8 −8 10 10 suppressed bottom Drell−Yan −9 −9 10 8 10 0 2 4 6 0 2 4 6 0 2 4 6 + − (GeV) M l l Lin, V ogt & W ang, PR C57,899(98) R WW'99, 1/9/99

Enhancemen t of dileptons from NA50 In termediate mass region: M > 1 : 5 GeV + � � � from Scomparin, SQM'98 R WW'99, 1/9/99

Enhancemen t from Charm Radial Flo w Hadron m in v erse slop e T mass: / T ef f 0 10 −1 10 −2 10 dN/m T dm T Final: 290MeV −3 10 −4 Initial: 160MeV 10 (PYTHIA) −5 10 0 1 2 3 4 2 m T −m D (GeV/c ) Then D-meson w ould b e harder: mid- p D-mesons enhanced. ? Ho w ev er, no c hange in the total n um b er R WW'99, 1/9/99

T Enhancemen t vs ef f 4 change of Dimuon yields (M>1.5GeV) 3 Final 2 Enhancement at SPS 1 Initial Simulated NA50 acceptance 0 150 200 250 300 350 D−meson T eff (MeV) Lin & W ang, PLB in press. Detailed study can b e done in a cascade mo del. Will this enhancemen t happ en at RHIC? p D D s Initial T Final T ef f ef f (GeV) (MeV, PYTHIA) (MeV) 17 (SPS) 160 290? 200 (RHIC) 430 5500 (LHC) 500 In addition to energy loss at RHIC, radial flo w ma y soften D-meson sp ectrum & lead to a SUPPRESSION of dileptons from c harm, instead of the enhancemen t at SPS. R WW'99, 1/9/99

Other Suggestions on IMR Dilepton Enhancemen t a A) � a annihilation : � 1 { enhancemen t comes mainly from the � a 1 coupling to � (1700); { ho w ev er, this coupling is uncertain b B) Secondary Drell-Y an pro cesses : � { mainly from in teractions b et w een pro duced mesons and bary ons sensitiv e to hadron formation time � { F e�ect v aries from 30% to 3 for P b + P b { Ho w to test these scenarios at RHIC? � 2 A) scales with (pion n um b er) { bigger enhancemen t at higher energies ) B) scales with (pion n um b er) { ho w ev er, �nite � w ould probably kill the F main con tribution due to the h uge � factor { Suppression exp ected from the op en c harm scenario a Li & Gale: Nucl.Ph ys.A638,491c(98) b Spieles et al, Eur.Ph ys.J.C5,349(98) R WW'99, 1/9/99

pA Op en Charm in at RHIC: a unique place to measure gluon shado wing c c � d� d � ^ Z Z pA 2 dxf ( x ) dx f ( x ) S ( x ; Q ) / A A A ^ 3 d p d t Nuclear shado wing of Large effects on quark densities observ ed. global observ ables at RHIC: Gluon shado wing to o(indirectly): (Ev en Larger effects on gluon-dominated pro cesses) Gousset & Pirner,PLB375,349(96). W ang & Gyulassy ,PRD44,3501(91) R WW'99, 1/9/99