Interesting Physics beyond the QGP discovery phase

Heavy flavor production Flavor dependence of QCD energy loss Jet studies and gluon-jet correlations in 4 Chiral Symmetry Restoration Onium Physics

R. Bellwied, February 2002R. Bellwied, February 2002

Interesting physics in the SPS dilepton spectrum

Dilepton Measurements: open charm production (D) charmonia suppression (J/) light mesons in dense matter

() thermal dimuons from QGP

Charm is a heavy flavor that is abundantly produced at RHIC

so These measurements provide the closest link to

pQCD, together with jet production at RHIC

No enhancement in pp and pA collisions

Strong enhancement of low-mass e+e- pairs in A-A collisions (compared to expected yield from known sources)

Enhancement factor (.25 <m<.7GeV/c2) : 2.6 ± 0.5 (stat) ± 0.6 (syst)

Low Mass Electron Pairs:

Chiral Symmetry Restoration ? (measure leptonic and hadronic decay channels)

The Intermediate Mass Region (IMR) excess: evidence from SPS (NA38/NA50)

pA: AA:

NA38+NA50

Properly described byDrell-Yan and D meson decays

and with a Total charm cross-

section consistent with previous direct measurements

IMR yield is higher than thesum of DY and D meson decays

in particular A factor 2 higher in

central Pb-Pb

Possible explanation for

IMR excess

Thermal radiation ?

Very good fit to databut

is a factor 3 charm enhancement conceivable ?

Good account for the IMR excesswhen added to expected sources

assuming QGP phase with Ti = 192 MeVMeasure Charm Enhancement at RHIC direct via hadronic decay channels

PHENIX Single Electron Spectra

PHENIX Single Electron Spectra

PHENIX Single Spectra Result

PHENIX Charm Yield Estimate

PHENIX Charm Yield Comparison

No Charm Enhancement necessary to explain RHIC data ?

A high precision vertex detectorwill allow a clean separation of charm and bottom decays

m c eX GeV m %

D0 1865 125 6.75D± 1869 317 17.2

B0 5279 464 5.3B± 5279 496 5.2

Need secondary vertex resolution ~ 30 - 50 mm

We need a direct measurement

of heavy flavor production

m c GeV m prime decay channel

D0 1865 125 K- + anything (54%), K-+ (4%)D± 1869 317 K-++ (9%),K0+ (3%)

B0 5279 464 K* J/B± 5279 496 K+ J/

CDF (Phys. Rev. D58 (1998) 072001) very successful in direct B-meson reconstruction using new defined isolation cut.

Decay channels for direct

measurement

D’s are relatively abundant (higher yield in STAR detector than1D/unit y))Even B-mesons be in our acceptance ~ once every ~100 events

Flavor dependence of QCD energy loss

Prediction by X.N.Wang et al.Phys.Rev.C 57 (1998) 899

Study flavor dependence of jet quenching (tag with identified high pT particle)

Important to extend spectra of identified charged particles out to as high pT as possible

Enhanced High pT

Physics

Flavor dependence of energy loss

Prediction by X.N.Wang,Phys.Rev.C 58 (1998) 2321

pt-dependence of ratios in STAR (based on year-1 data)

Need high pt !! (will get a little more from statistics in years-2+(based on existing RICH for p and topology analysis for )

How to measure a high pt spectrum

For the primaries you need PID out to large pt (see next slide)

For the secondaries you can use the topology method out to large pt without PID (to some extent). E.g. the spectrum in STAR will reach out to about 5 GeV/c.

You need precision tracking for D-meson and B-meson reconstruction.

Extended PID with Aerogel

Aerogel together with TOF can extend the PID capability up to ~ 10 GeV/c

5 - 91 - 5 n=1.007Aerogel

17 -5 - 17 n=1.004RICH

0 - 50 - 2.5 ~100 ps

TOF

Kaon-Protonseparation

Pion-Kaonseparation

0 4 8

0 4 8

0 4 8 0 4 8

0 4 8

0 4 8

Y. Miake

Forward Physics in STAR

Charged hadron and lepton (?) spectra (pt and rapidity) between h = 2.5-4.0 for AA and pA collisions.

Separate peripheral collision program Important jet physics program in pp and pA. V0 reconstruction (without PID) Possibly better phase space for D-meson mass

reconstruction through charged hadron channel

Bellwied, RHIC workshopBellwied, RHIC workshop

More Forward Physics Goals

Measurements in the baryon-dense regime In central collisions the forward region will be baryon-

rich (high baryochemical potential). Exotic phenomena, e.g. centauro-like events and strangelets, are preferably produced in such an environment..

production of light nuclei and antinuclei carries information of baryochemical potential and of production mechanism in baryon-rich region compared to baryon-poor mid-rapidity region.

anti-proton suppression due to increased annihilation ?

Bellwied, RHIC workshopBellwied, RHIC workshop

Precision Measurements: Tagged Jet quenching

Direct -tagged events: E~Ejet

Compare AA to pp Need to measure pT spectrum

of particles opposite high ET or 0 ?

Need to do this vs Species/Energy to find energy

loss How big? Proportional to mean free

path? Gluon/quark difference

PT

Reaction Plane

jet

Collision axis

Large back to back coverage:EMCAL and tracking & high pt pid in 4

would be ideal

Tomography? (penetrating probes)(from Richard Seto’s talk)

Do as a function of “position” I.e. many bins of centrality, pt, y, reaction plane E.g

Jet energy loss Mass shift Other? (J/ Suppresssion/charm enhancement)

Requires Very High statistics

E.g. 10 bin in pt, 5 bins in y,5 bins in centrality, 8 bins in reaction plane

400 points per centrality; 2000 points Good geometry measurements

Reaction plane/centrality – event by event

Summary There is interesting physics in the heavy flavor production (s, c, b)

that is not achievable with the present STAR detector. In particular the D- and B-meson cross section and the pt-spectrum

of strange, charm and bottom particles ( flavor dependence of QCD energy loss)

Jet studies and gluon-jet correlations will benefit from 4coverage In terms of continuation of original measurements:

Measure lepton and hadron decay channels of vector mesons in parallel (chiral symmetry restoration)

-> Tomography of the QGP source

Detectors we need

High pt PID in 4 RICH, Aerogel and TRD detectors

High precision vertexing at central rapidity Active pixel or CDD layers

High precision tracking in 4 Forward tracking with straw-tubes or Silicon

-> See Howard’s Talk

• Separation of charm/bottom decays by measuring displaced secondary vertex improve measurement accuracy of c and b cross sections to < 10% separate c and b contribution in each pT bin (flavor dependence of QCD energy loss)

• Direct measurement of D mesons combined with particle id, can measure D -> Kp modes => pT spectrum of D’s (flavor dependence of QCD energy loss)

• Improved momentum resolution for Upsilon spectroscopy

• Enhanced capabilities for spin physics wider acceptance (g-jet & jet-jet studies, c,b-tagging, etc)

• Enhanced physics capabilities for charm and bottom in pA

Enhanced Physics Capabilities with

a

High Precision Vertex Tracker

PHENIX Background Subtracted Spectra