Recent results from relativistic heavy ion collisions

Transcription

1 Recent results from relativistic heavy ion collisions Camelia Mironov MI at the LHC A teaser talk with very few (though recent) results

2 LHC Heavy-Ion (HI) Program Collision systems Center of mass colliding energy (ev).76 (11, 13) 5. (15) 7,13 5. (13).76 (1, 11) 5. (15)

3 Characterize HI collisions A A 5 Event-activity characteristics (Data, Monte Carlo) central collisions: small impact parameter collision (high-multiplicity events, large energy deposited in calorimeters, etc) peripheral collision: large impact parameter collision At a certain colliding energy, for a certain impact parameter b <Npart> number of incoming nucleons participating in the collision <Ncoll> number of equivalent nucleon-nucleon collisions - Glauber MC calculation 3

4 Characterize HI collisions Particle production transverse momentum: component perpendicular on the beam axis - p = p cosθ pseudorapidity: angular position in detector = ln[tan( /)]

5 /dη ch dn part N LHC vs RHIC 1 pp(pp), INEL AA, central 1 ALICE ALICE CMS CMS UA5 ALAS 1 PHOBOS PHOBOS ISR PHENIX.155() BRAHMS s 8 pa(da), NSD SAR ALICE NA5 6 PHOBOS PRL 116 (16).13() s η <.5 1 s NN (GeV) he charged particle multiplicity per colliding nucleon pair measured at LHC for the most central collisions is ~x that measured at RHIC, where the collision energy is factor 1 lower ~x that measured at LHC in pp or ppb collisions at similar collision energy 5

6 Analyzing HI collisions: -particle correlations rigger particle p trig,η trig, φ trig CMS pp 1 < p φ s = 13 ev, N < 3 GeV/c offline trk < η (a) pair N d d η d φ 1 N trig Associated particle p asssoc,η assoc, φ assoc Event-by-event Back-to-back jet contribution 3 φ (radians) η Single jet contribution 3 Δη = η trig - η assoc ΔΦ = φ trig - φ assoc 6

7 Collective motion: -particle correlations Back-to-back jet contribution Single jet contribution RIDGE: collective effect particles with very different η are connected JHEP 9 (1) 7

8 Collective motion: -particle correlations (b) CMS ppb offline s NN = 5. ev, N trk PLB 718 (13) < 6 1 < p 1 < p trig assoc < 3 GeV/c < 3 GeV/c d N d η d φ pair 1 N trig RIDGE Also in ppb highmultiplicity events φ (radians) - - η Back-to-back jet contribution Single jet contribution RIDGE: collective effect particles with very different η are connected JHEP 9 (1) 8

9 PLB 718 (13) Collective motion: ppb PLB 719 (13) ALICE arxiv: arxiv:151.39

10 Collective motion everywhere! offline (b) CMS ppb trig 1<p pair < 6 < 3 GeV/c passoc 1 dn Ntrig d η d φ 1< snn = 5. ev, Ntrk < 3 GeV/c φ RIDGE Also in pp highmultiplicity events (ra di an s ) η - - Single jet contribution pair 1 dn Ntrig d η d φ Back-to-back jet contribution CMS pp s = 13 ev offline 15 Ntrk < 15 trig assoc 1<p,p < 3 GeV/c h± - h± RIDGE: collective effect particles with very different η are connected φ 1 (ra di an JHEP 9 (1) s) CMS-PAS-FSQ5- ALAS-CONF6-6 η

11 LHC: 5.eV Z Z inclusive jet / identified-jet l + l - l + l - Q r,δe Q h/d/b inclusive jet inclusive jet / identified-jet A) Individual hadrons B) Reconstructed jets C) Quarkonia Questions one addresses with these measurements Is there a difference in how the light partons and heavy (charm and beauty) quarks interact with the medium? What are the properties of the medium created? 11

12 Analyzing HI collisions: R AA R AA = Yield(A + A) Yield(p + p) <N coll > Nuclear modification factor: if = 1 no medium effects if < 1 suppression (e.g. energy loss in the medium) if > 1 enhancement (e.g. k broadening in the incoming nuclei) 1

13 Z boson: in-situ reference PRL 11 (13) R AA.5 CMS s NN =.76 ev Z ll, y < 1., p > GeV/c Z ll, % centrality pp luminosity uncertainty JHEP 3 ( Z N part Z boson measured for the first time in HI collisions confirm the Ncoll scaling: R AA = 1 l + l - 13

14 Charged hadrons (gluons & u/d/s quarks) pb (5. ev pp) + µb CMS Preliminary AA and lumi. uncertainty η <1 CMS 5. ev CMS.76 ev ALAS.76 ev ALICE.76 ev (5. ev PbPb) CMS-PAS-HIN55 R AA % 1 1 p (GeV) 1 Agreement between experiments at.76ev And same suppression at.76ev and 5eV 1 h

15 D mesons (charm quarks) JHEP 9 (1) CMS-PAS-HIN6 ) Entries / (5 MeV/c π CMS Preliminary PbPb s NN = 5. ev Data y < < p < 3. GeV/c Fit 18 Centrality % D +D Signal 16 K-π swapped 1 Combinatorial K m πk (GeV/c ) D D decay vertex Primary 15 D

16 Charm vs Light JHEP 3 (16).76 ev 5. ev R AA D CMS Preliminary AA and lumi. uncertainty R AA R AA µ D Centrality % y < 1 CMS-PAS-HIN6 CMS-PAS-HIN55 charged hadrons p (GeV/c) 1 At high-p (~-5GeV/c) light partons (quarks and gluons) and charm quarks products have same R AA 16

17 B(J/ψX) mesons (beauty quark) CMS-PAS-HIN ) Events / (. GeV/c CMS Preliminary PbPb s NN L int = 15 µb y <. 6.5 < p < 3 GeV/c Cent. % =.76 ev N J/ψ : 855 ± 177 σ = 35 ± 1 MeV/c data total fit bkgd + non-prompt background B L xy µ J/ψ µ + Events / (.35 mm) CMS Preliminary PbPb s NN =.76 ev L int = 15 µb y <. 6.5 < p < 3 GeV/c Cent. % data total fit bkgd + non-prompt background ) Entries / ( MeV/c PRL 116 (16) CMS + - B +B m B m µµ (GeV/c ) 3.6 nb 1 < p (GeV/c (ppb 5. ev) < 15 GeV/c y <. lab Data Fit Signal Combinatorial B J/ψ X ) ) Entries / (3 MeV/c CMS B B + +B m = 3.1 GeV/c cτ = 9 µm 3.6 nb J/ψ B + Decay Vertex First b-quark Combinatorial products 3 measurement B J/ψ+X First exclusive B reconstructed in pa collisions B J/ψ+K m B µ + 1 < p Data Fit Signal (GeV/c B J/ψ X ) µ - (ppb 5. ev) < 15 GeV/c y <. lab K + ) Entries / ( MeV/c CMS B s +B s m B l J/ψ (mm) m J/ J/ = L xy 3.6 nb (ppb 5. ev) 1 < p < 6 GeV/c p y <. lab Data Fit Signal (GeV/c Combinatorial )

18 Beauty vs Charm vs Light JHEP 11 (15) B J/ψ D, h Smaller measured suppression between the b-quark products and charm or gluon/light-quarks products 18

19 Fully reconstructed jets in the kinematic regions where we can 19

20 Z+jet: in-situ reference CMS-PAS-HIN53 Z l + l - Jet Central PbPb x JZ distributions shifted to lower values wrt pp at all Z-p : the back-parton suffers energy loss in the medium theoretical models: energy loss directly related to the medium density

21 CMS-PAS-HIN6-5 Jet 1 Jet J x x J = pjet p Jet pb (5. ev pp) + µb pp 3% Inclusive dijets Data Beauty vs Light pp-based reference 1-3% N (N -weighted) part coll (5. ev PbPb) CMS Preliminary % J x p Jet p Jet pp > GeV/c > 1GeV/c 5.8 pb (5. ev pp) + µb b dijets 3% Data pp-based reference 1-3% N (N -weighted) part coll (5. ev PbPb) CMS Preliminary % b-jet 1 b-jet Blue: Inclusive-dijets imbalance increases from peripheral to central PbPb collisions Red: Imbalance of b-dijets measured for the first time similar to that of inclusive jets (red vs blue) 1

22 LHC: the full picture *Z (%) y < µ µ W (%) p > 5 GeV/c, η <.1 Isolated photon (%) η < 1. Charged particles (-5%) η < 1 *B J/ψ (%) y <. Photons, W, Z 1.5 CMS *PRELIMINARY PbPb L dt = 75 µb *Inclusive jet (-5%) η < *b-jet (%) η < s NN =.76 ev R AA !, h, D h, B J/ψ p (m ) [GeV] p Inclusive jet, b-jet [GeV] Probes blind to the medium: photons, Z, W Probes affected by the medium: low-p: different suppression pattern for b-quark vs c/q/gluon products high-p: similar suppression pattern no matter the color of the pattern

23 Quarkonia Q r,δe Q A. Mocsy Eur.Phys.J.C61,8 Onia in a deconfined partonic medium: color screening at different medium temperatures for different states (depending on binding energy) sequential melting/destruction of the states Onia: thermometer of the medium 3

24 Sequential melting: ϒ(1S, S, 3S) PRL 19 (1) R AA 1. CMS PbPb =.76 ev s NN 1. 1 ϒ(1S) ϒ(S) ϒ(3S), 95% upper limit PbPb L int = 15 µb pp L int = 3 nb.8.6 5% -5% 3-% -3% 1-% 5% -5% % N part R AA Υ(1S) > R AA Υ(S) > R AA Υ(3S) A. Mocsy Eur.Phys.J.C61,8 Sequential melting (proposed as key proof for existence of a QGP), first experimental proof of color screening picture

25 Quarkonium phenomena: J/ψ JHEP 5 (16) R AA 1. CMS Preliminary PbPb =.76 ev s NN CMS-PAS-HIN 1. Low-p 1.8 Prompt J/ψ.6. Regeneration High-p p (GeV/c) Cent. % y <. Parton/jet fragmentation and en loss Puts back some QQbar Destroys and/or shifts the kinematics via partonic/hadronic interactions Experimental confirmation of (old) theoretical ideas 5

26 pp, ppb, PbPb ϒ(S)/ϒ(1S).5.5. pp s NN =.76 ev y < 1.93 CM ppb s NN y < 1.93 CM = 5. ev PbPb s NN y <. CM =.76 ev JHEP (1).35.3 ϒ(S) ϒ(1S) CMS 1 Low rack Multiplicity < p < GeV/c 1 η <. N tracks 3 1 High rack Multiplicity Sequential patterns also in pp & ppb not clear whether it was the medium affecting the states (as in PbPb), or the state affecting the medium 6

27 Υ(S)/Υ(1S) CMS Preliminary.8 fb Υ(S)/Υ(1S) p (7 ev) < 5 GeV (.3 fb ) 5 p < 7 GeV (1.9 fb ) 7 p < 9 GeV 9 p < 11 GeV 11 p < 13 GeV 13 p < 18 GeV 18 p < 5 GeV 5 p 5 GeV CMS-PAS-BPH-9 5 < p < 5 GeV/c < p < 5 GeV/c.1 y(µµ) < Low rack Multiplicity η <. N tracks Decrease of the excited/ground state ratio confirmed at 7eV he ratio decreases strongly at lower p High rack Multiplicity in PAS: stronger indications that it is not the state affecting the medium 7

28 LHC heavy-ions: Summary Precision, Diversity and Surprises Precision: - charged hadrons measured up to GeV/c - separate measurements of charm & beauty quarks products Diversity - identified hadrons AND fully reconstructed jets Surprises: - collectivity also in ppb and pp collisions - sequential pattern for onia also observed in pp and ppb collisions 8

29 Extra stuff 9

30 LHC: collective motion EVERYWHERE CMS Preliminary.1 pp s = 13 ev sub {, η >} v v {} v {6} v {8} v {LYZ} ppb s NN = 5 ev PbPb s NN =.76 ev v.5.3 < p η < offline N trk < 3. GeV/c.3 < p η <. offline N trk < 3. GeV/c < p η <. 1 3 offline N trk < 3. GeV/c (6, 8) -particle cumulant (average over all events). c n {} =, v n {} = c n {} 1 z arxiv: cos n( φ 1 +φ φ 3 φ ) #$ % & 3