News on Hadrons in a Hot Medium Mikko Laine (University of - PowerPoint PPT Presentation

News on Hadrons in a Hot Medium Mikko Laine (University of Bielefeld, Germany) 1

How to interpret the title? “Hot Medium”: 50 MeV ≪ T ≪ 1000 MeV; µ ≪ πT . “Hadrons”: In this talk only those which maintain their identity... “News”: Statistics on references: 2004: x 2005: x 2006: x x x x 2007: x x x x x x x 2008: x x x x x x 2009: x x x x x x x 2010: x x x x x x x x x x x x 2011: x x x x x x x x x x 2

Outline (i) “Open c, b ”: D, B mesons. c, b ¯ (ii) “Bound c ¯ b ”: J/ Ψ , Υ mesons. c, b ¯ (iii) “Virtual c ¯ b ”: pairs from thermal fluctuations. Apologies to π, K, η, ρ, ω, ... ! [cf. parallels & posters] 3

Open c, b Copiously produced in an initial hard process: c, b c, ¯ ¯ b e.g. Cacciari et al hep-ph/0502203 What happens afterwards? 4

Particularly interesting is propagation through a medium The heavy quark jets tend to get slowed down and eventually stopped, by bremsstrahlung as well as by elastic scatterings. In the latter case some gluons can be off-shell and soft, leading to large infrared effects: 5

Indeed less D → K observed than expected: The D meson R AA (0-20%) � Suppression for charm is a factor 4-5 above 5 GeV/ c Quark Matter 2011, Annecy, 27.05.11 Andrea Dainese 31 6

The same is the case for muons from B decays: Muon R AA at forward rapidity 40-80% 0-10% � Suppression is of about a factor 3 above 6 GeV/ c � According to FONLL, beauty dominant in this region Quark Matter 2011, Annecy, 27.05.11 Andrea Dainese 38 7

Recent theoretical literature LO and NLO pQCD at T ≫ 200 MeV: Moore Teaney hep-ph/0412346; Caron-Huot Moore 0708.4232; 0801.2173. Model studies at T ≫ 200 MeV: van Hees et al 0709.2884; ML et al 0902.2856; Riek and Rapp 1005.0769. Non-perturbative formulation within QCD: Casalderrey-Solana Teaney hep-ph/0605199; Caron-Huot et al 0901.1195. Towards lattice measurements: Highlight Burnier et al 1006.0867; Meyer 1012.0234; Burnier et al 1101.5534. Chiral effective theory studies at T ≪ 200 MeV: Highlight ML 1103.0372; He et al 1103.6279; Ghosh et al 1104.0163; Abreu et al 1104.3815. Hydrodynamic + Langevin simulations: Moore Teaney hep-ph/0412346; and very many follow-ups. 8

Highlight 1: Towards lattice measurement 3 G E ( τ ) = − 1 � Re Tr[ U β ; τ gE i ( τ, 0 ) U τ ;0 gE i (0 , 0 )] � � . 3 � Re Tr[ U β ;0 ] � i =1 α s 0.01 0.05 0.1 0.2 0.3 0.4 100 0.6 8x32 3 , T/T c =6.2 Next-to-leading order (eq. (2.5)) 12x64 3 , T/T c =4.1 Leading order (eq. (2.4)) 0.5 16x64 3 , T/T c =3.1 Truncated leading order (eq. (2.5) with C=0) 22x64 3 , T/T c =2.2 0.4 O(g 4 ) [1006.0867] κ/g 4 T 3 G E (t) / T 4 10 0.3 0.2 0.1 0 1 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.5 1 1.5 2 2.5 T t g s Caron-Huot Moore 0801.2173 Meyer 1012.0234 ⇒ Huge pQCD effects almost hidden on the Euclidean lattice! 9

Highlight 2: T ≪ 200 MeV Interactions strong when “diffusion coefficient” 2 πT D x is small. 100 90 Ds_Rapp.jpg.dat This work This work 80 Laine Laine 70 He, Fries, Rapp He, Fries, Rapp 60 x Rapp, van Hees Rapp, van Hees T D 50 π 40 2 30 20 10 0 0 50 100 150 200 250 300 350 400 T (MeV) Abreu et al 1104.3815 ⇒ Strong effects could continue deep into the hadronic phase! 10

c, b ¯ Bound c ¯ b Initial production: q ℓ + Subsequent thermally modified decay: q ¯ ℓ − 11

Quarkonium states as visible in the µ + µ − spectrum: Compact Muon Solenoid: � + � - invariant mass Z. Hu (TODAY), T. Dahms (Tue), C. Silvestre (Fri), J. Robles (Fri), M. Jo (Poster), D.H.Moon (Poster), H. Kim (Poster) Bolek Wyslouch (LLR/MIT) Overview of CMS experimental results 20 12

A possible thermal modification of the spectral shape: Suppression of excited � states pp PbPb � 0 . 16 � 0 . 13 � ( 2 S � 3 S ) � ( 1 S ) � 0 . 78 � 0 . 02 � ( 2 S � 3 S ) � ( 1 S ) � 0 . 24 � 0 . 02 pp � 0 . 14 PbPb � 0 . 12 � ( 2 S � 3 S ) � ( 1 S ) PbPb � 0 . 19 � 0 . 31 � 0 . 03 � 0 . 15 ( 2 S 3 S ) ( 1 S ) � � � pp • Excited states � (2S,3S) relative to � (1S) are suppressed • Probability to obtain measured value, or lower, if the real double ratio is unity, has been calculated to be less than 1% Z. Hu (TODAY), C. Silvestre (Fri) Bolek Wyslouch (LLR/MIT) Overview of CMS experimental results 24 13

A slight paradigm shift concerning thermal physics Traditional view: it remains a q coherent QM bound state but in a Debye-screened potential. ¯ q Modern view: coherence is (partly) lost due to random kicks from a heat bath; static potential might develop an imaginary part. 14

Recent theoretical literature (in the “modern” direction) Complex real-time static potential ML et al hep-ph/0611300; 0707.2458; 0903.3467; Beraudo et al 0712.4394; Dumitru et al 0903.4703; Noronha Dumitru 0907.3062; Philipsen Tassler 0908.1746; Chandra Ravishankar 1006.3995; Margotta et al 1101.4651. Full-fledged effective field theory formulation (“PNRQCD HTL ”) Escobedo Soto 0804.0691; 1008.0254; Brambilla et al 0804.0993; 1105.4807 Spectral function and thermal part of d N µ − µ + / d 4 x d 4 Q Highlight ML 0810.1112; Burnier et al 0711.1743; 0812.2105; Grigoryan et al 1003.1138; Riek Rapp 1005.0769; Miao et al 1012.4433. Highlight Bottomonium below melting; its velocity dependence Brambilla et al 1007.4156; Dominguez Wu 0811.1058; Escobedo et al 1105.1249. Lattice (within full QCD or effective theory) Highlight Jakovac et al hep-lat/0611017; Aarts et al 0705.2198; Rothkopf et al 0910.2321; Aarts et al 1010.3725; Ding et al 1011.0695. 15

Highlight 1: from “on-off” melting towards spectral shape Qualitatively ( b ¯ b ): 4 x d 4 Q d N µ + / d − µ -16 10 150.0 T = 500 MeV " b i n d -18 i 10 n T = 400 MeV g e n e r T = 350 MeV 100.0 g -20 10 y "decay width" " MeV ⇒ T = 300 MeV -22 10 50.0 -24 T = 250 MeV 10 -26 10 M = 4.5 ... 5.0 GeV 0.0 200 250 300 350 400 1.6 1.8 2.0 2.2 2.4 T / MeV ω /M ML et al hep-ph/0611300 Burnier et al 0812.2105 at low T (far below “melting”) width rises Quantitatively : linearly with T and its velocity-dependence is also computable. Brambilla et al 1007.4156; Escobedo et al 1105.1249 16

Highlight 2: lattice computations within effective theories Either determine the spectral function through a lattice simulation within “NRQCD” ... Aarts et al 1010.3725; in progress ... or determine a real-time static potential V > ( ∞ , r ) , perhaps to be used within “PNRQCD HTL ”, through spectral analysis of an imaginary-time Wilson loop. Rothkopf et al 0910.2321; in progress Position: Re V > ( ∞ , r ) . Width: Im V > ( ∞ , r ) . 17

c, b ¯ Virtual c ¯ b from thermal fluctuations When is T high enough for quarks to “chemically equilibrate”, i.e. to be part of the heat bath? Naively: T ≫ 2 m , so that there is no Boltzmann suppression, exp( − 2 m T ) , of pair creation of a quark-antiquark pair. But should one use here m MS ( 3 GeV ) ≈ 1 GeV, c m pole ∼ (1 . 5 − 2 . 0) GeV, or something else? c And should the comparison be with T or 2 πT or ...? 18

There are effects visible at surprisingly low T ! lattice (w/o extrapolations) pQCD 10 - ) 6 ln 1 2 ) charm O(g g N f = 3 + O(g 8 - ) 6 ln 1 O(g g N f = 3 6 4 (e - 3p) / T 4 2 0 200 300 400 500 600 700 800 900 1000 T / MeV DeTar et al 1003.5682 ML Schr¨ oder hep-ph/0603048 (Cheng et al 0710.4357, Borsanyi et al 1007.2580) ⇒ Perhaps relevant for initial stages of hydrodynamics @ LHC? 19

Conclusions In heavy ion collisions at the LHC, various heavy-quark related observables are increasingly important and may turn out to yield versatile information about the dynamics of hot QCD. Much well-defined work remains to be carried out! 20