Light vector mesons from d Au in PHENIX

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Light vector mesons ( ) from d. Au in PHENIX Richard Seto University of

Light vector mesons ( ) from d. Au in PHENIX Richard Seto University of California, Riverside for the PHENIX Collaboration Quark Matter 2004 January 13, 2004 9/15/2020 1

QCD and the vacuum n 2 The QCD Lagrangian ~ chiral symmetry (Is it

QCD and the vacuum n 2 The QCD Lagrangian ~ chiral symmetry (Is it true? ) all masses ~0 n n Doesn’t match the world we know What do we do? n n n Assume the vacuum is not empty – it full of stuff (the “condensate”) The interaction with the vacuum gives rise to mass Condensate is Temperature dependent n I. e. at high T all masses ~ 0 Crazy!? Can we test this idea? Heat up the vacuum in RHIC collisions – we boil it - and see if masses change n n go to zero ultimately Chiral phase transition Any connection to deconfinement? ? T>Tc Nothingness T<T T~T cc Hot Vacuum ~ early universe

3 Looking for Chiral symmetry restoration Vector Meson mass shifts in the dilepton channel

3 Looking for Chiral symmetry restoration Vector Meson mass shifts in the dilepton channel n “Light” Vector mesons ( , , )-ideal probes n n n Electrons are ideal messengers n n Like putting a scale to measure mass inside the fireball Short lifetime ~ few fm/c Decay inside hot fireball Don’t interact strongly (e. g. solar ’s) e. g. In Medium n , , shows low mass tail n With its good mass resolution PHENIX should be able to see this R. Rapp (Nucl. Phys A 661(1999) 238 c e+ e-

Experimental “Knobs” n Signal should increase with centrality n Signal should increase at low

Experimental “Knobs” n Signal should increase with centrality n Signal should increase at low pt Central“High” PT Peripheral com Central 4 Me+e pare Me+e Central“Low” PT signal Me+e n Me+e Today : d. Au – min bias only – but there is a “trick” : Au-Au – function of centrality

What do we look for? n Chiral symmetry restored n n High temperature vacuum

What do we look for? n Chiral symmetry restored n n High temperature vacuum – Au-Au Central High baryon density n n even normal nuclear density. Look for n n Mass shifts/broadening A nice trick: n n Q value of KK is small Should be sensitive to mass changes in either or K Lissauer and Shuryak, Phys. Lett. B 253, 15 (1991). T. Hatsuda and S. Lee QCD sum rules for vector mesons in the nuclear medium (Phys. Rev. C 46 -R 34 -38, 1992) 5

Has anyone seen such effects? 6 e+e- invariant mass spectra n CERES Pb-Au n

Has anyone seen such effects? 6 e+e- invariant mass spectra n CERES Pb-Au n High T vacuum From QM 2002 courtesy of I. Tserruya n KEK E 325 – proton Nucleus n “high” baryon density K. Ozawa et al. Observation of r/v Meson Modification in Nuclear Matter (Phys. Rev. Lett 86 -22)

Let’s Look at RHIC (PHENIX) 7 Outline n Compare BR (normal nuclear density) n

Let’s Look at RHIC (PHENIX) 7 Outline n Compare BR (normal nuclear density) n n n d. Au ee d. Au KK Mass shifts/broadening n Au-Au KK n n Guess: cannot see this to hadronic decays (only see stuff which decays outside fireball) – or the kaons which do decay and make it out rescatter Centrality dependence of /Npart Note: I will not talk about RCP – see talk by D. Kochetkov: Friday parallel session 2

8 d. Au Collisions: comparing the at normal nuclear density in PHENIX @ RHIC

8 d. Au Collisions: comparing the at normal nuclear density in PHENIX @ RHIC

PHENIX– designed for such measurements n Superb (and redundant) electron PID n n n

PHENIX– designed for such measurements n Superb (and redundant) electron PID n n n PID (for kaons) n n n EMC(PBSc, Pb. Gl) RICH Via TOF to 2 Ge. V Via EMC to 1 Ge. V Good momentum resolution High rate capability Triggering capability on electron at Level-1 n n EMC-RICH-Trigger (ERT) Require energy in EMC+RICH firing in coincidence Need everything working in concert to get a di-electron low mass vector Meson measurement! 9

Data sample, electron cuts n Analyzed 31 M of EMCRICH-Trigger triggered Events. n n

Data sample, electron cuts n Analyzed 31 M of EMCRICH-Trigger triggered Events. n n n Energy / Momentum Corresponds to 1. 9 G minimum bias 50% of total data taken during run 3 Threshold > 600 Me. V Electron PID cuts NRICH PMT 2 0. 5<E/p<1. 5 n n E - from EMC P - from tracking 10 NRICH PMT 2 0 1 E/p 2

11 Conversion cuts, mixed background Sidebands for background normalization Phi. V ( 100<mass<400 Me.

11 Conversion cuts, mixed background Sidebands for background normalization Phi. V ( 100<mass<400 Me. V ) Mixed n Rejecting conversions n Phi. V=Angle plane of pair makes with plane normal to beam direction n Mixed Background Zero mass pairs Phi. V~0 Reject conversion pairs if n Counts per 10 Me. V/c 2 Cut If Mee<100 If 100<Mee<400 and phi. V<100 mrad e+e- invariant mass (Ge. V/c 2)

12 n n N ~120 Fit is to relativistic B-W convoluted with Gaussian n

12 n n N ~120 Fit is to relativistic B-W convoluted with Gaussian n n M=1. 0177 0. 0023 Ge. V =0. 00446 Ge. V(fixed) exp=0. 0081 0. 0021 Ge. V 2/DOF=13. 6/13 Consistent with PDG Counts per 10 Me. V/c 2 ee Invariant Mass Spectra 200 Ge. V d. Au- all m. T e+e- invariant mass (Ge. V/c 2) n Now n break into 3 m. T bins n count signal by summing mass bins 3 around mass peak n Do corrections and Poster: Electro 4 Yuji Tsuchimoto

1/2 m. T d. N/dm. Tdy (Ge. V/c 2)-2 d. N/dm. T and yield

1/2 m. T d. N/dm. Tdy (Ge. V/c 2)-2 d. N/dm. T and yield d. Au e+e- 13 d. N/dy=. 056. 015(stat) 50%(syst) T=326 94(stat) 53%(syst) Me. V (PHENIX preliminary) • major contributions to the systematic error PHENIX preliminary MT(Ge. V/c 2) • normalization of the background and signal extraction and the way the variations affect T and hence d. N/dy • run-by run variation from the Electron-RICH -Trigger

200 Ge. V d. Au – K+K- invariant mass n PID in TOF only

200 Ge. V d. Au – K+K- invariant mass n PID in TOF only (smaller acceptance) n n 14 Higher pt Nevt = 62 M Min. bias Fit to Relativistic BW convoluted with a Gaussian n N = 207 16 S/B ~ 5/1 m= 1. 0193 0. 0003 Ge. V/c 2 n n Momentum scale error ~1% = 4. 750 0. 67 Me. V/c 2 =1. 2 Me. V (fixed) PDG M=1. 01946 Ge. V/c 2 = 4. 26 Me. V/c 2 Poster: Spectra 9 Dipali Pal

1/2 m. T d. N/dm. Tdy (Ge. V/c 2)-2 Minimum-bias m. T distribution of

1/2 m. T d. N/dm. Tdy (Ge. V/c 2)-2 Minimum-bias m. T distribution of d. Au ee d. Au KK KK min bias d. N/dy = 0. 0468 +/- 0. 0092(stat) (+0. 0095, -0. 0092) (syst. ) T (Me. V) = 414 +/- 31 (stat) +/- 23 (syst) (PHENIX preliminary) PHENIX preliminary MT(Ge. V/c 2) 15 Overall fit d. N/dy~. 0485 T~408 2/DOF=6. 7/7

Compare ee with KK results KK channel d. N/dy = 0. 0468 +/- 0.

Compare ee with KK results KK channel d. N/dy = 0. 0468 +/- 0. 0092(stat) (+0. 0095, -0. 0092) (syst. ) ee channel d. N/dy=. 056. 015(stat) 50%(syst) KK ee KK channel T (Me. V) = 414 +/- 31 (stat) +/- 23 (syst) ee channel T=326 94(stat) 53%(syst) Me. V T T(Me. V) d. N/dy 16 n Yields consistent with each other n KK ee BR in normal ratio PHENIX preliminary

17 Au-Au collisions: to KK mass and width dependence on centrality

17 Au-Au collisions: to KK mass and width dependence on centrality

Au-Au to KK Min bias PID in EMC +TOF only 18 n study the

Au-Au to KK Min bias PID in EMC +TOF only 18 n study the mass and width as a function of centrality n Min bias Fit to Relativistic Breit Wigner convoluted with a Gaussian experimental resolution n =1. 2 Me. V from MC Poster: Strange 14 Charles Maguire

Mass (Ge. V/c 2) Mass=1. 01876. 00012(stat) Ge. V/c 2 Systematic error= 0. 85

Mass (Ge. V/c 2) Mass=1. 01876. 00012(stat) Ge. V/c 2 Systematic error= 0. 85 Me. V from Momentum scale uncertainty ~1. 7% 19 n Mass consistent with PDG n independent of centrality- n Width consistent with PDG n Independent of centrality Note: KK decaying in fireball – scattered out of peak n PHENIX Dependence of mass and width on centrality PDG M=1. 01946 Ge. V/c 2 = 4. 26 Me. V/c 2 (Ge. V/c 2) Npart KK Au-Au 200 Ge. V 2 2 =3. 97 0. 34(stat) =3. 97 0. 34 (stat) Ge. V/c Me. V/c PHENIX Npart

20 more standard fare: Yields and slopes in d. Au and Au. Au

20 more standard fare: Yields and slopes in d. Au and Au. Au

21 Yields and slopes: Centrality dependence Min bias d. N/dy=1. 34 0. 09(stat) 0.

21 Yields and slopes: Centrality dependence Min bias d. N/dy=1. 34 0. 09(stat) 0. 20(syst) T=366 11(stat) 18(syst) Me. V 0 -10% on correct scale, others offset by factors of 10 1/2 m. T d. N/dm. Tdy (Ge. V/c 2)-2 Au. Au K+K- 0 -10% 10 -40% 40 -92% PHENIX MT(Ge. V/c 2)

Npart dependence of T T(Me. V) Au-Au – PHENIX FINAL d. Au – PHENIX

Npart dependence of T T(Me. V) Au-Au – PHENIX FINAL d. Au – PHENIX prelim Au. Au KK d. Au ee T indep of centrality Npart 22

d. N/dy per participant d. N/dy per Npart (Npart~9) 23 Au. Au KK d.

d. N/dy per participant d. N/dy per Npart (Npart~9) 23 Au. Au KK d. Au ee Au-Au – PHENIX FINAL d. Au – PHENIX prelim d. N/dy rises than seems to saturate Npart

d. N/dy per participant Add kaons Au. Au K – published (nucl-ex/0307022) Au-Au phi

d. N/dy per participant Add kaons Au. Au K – published (nucl-ex/0307022) Au-Au phi to KK– PHENIX FINAL d. Au – PHENIX prelim Au. Au KK Kaon arbitrarily normalized d. Au KK d. Au ee Au. Au (K++K-)/2 d. N/dy rises than seems to saturate as do the kaons Npart 24

Conclusion d. Au e+e- d. N/dy=. 056. 015(stat) 50%(syst) T=326 94(stat) 53%(syst) Me. V

Conclusion d. Au e+e- d. N/dy=. 056. 015(stat) 50%(syst) T=326 94(stat) 53%(syst) Me. V d. Au K+K- d. N/dy = 0. 0468 +/- 0. 0092(stat) (+0. 0095, -0. 0092) (syst. ) T (Me. V) = 414 +/- 31 (stat) +/- 23 (syst) • Summary: • A first measurement has been made of the to ee channel in d. Au collisions at 200 Ge. V. Within error bars it agrees with the KK result. • For overall shapes in Au-Au to KK, mass and width stay consistent with PDG as a function of centrality • Enhancement as a function of centrality, similar to kaons 25

Outlook to the future Note: early in the story of lmvm ee physics at

Outlook to the future Note: early in the story of lmvm ee physics at RHIC n Near term : this data n n n run 4 n n n Use rest of statistics (ert threshold>800 Me. V, min bias) Better control of systematics Centrality, pt dependence (d. Au-KK, ee? ) omega flow (poster Flow 7: Debsankar Mukhopadhyay) ee in Au-Au 50 x run-2 The far future n n Upgrades- the Hadron Blind Detector (Cerenkov) RHIC II 26

Full data sample – the future 27

Full data sample – the future 27

Behavior of K, p, pi n n Pion – yellow Proton – green Kaon

Behavior of K, p, pi n n Pion – yellow Proton – green Kaon - lightblue Phi-Black+red+blue 28