LANL work on Au+Au data

1. LANL work on Au+Au data • MVD past, present, future • J/Y->m+m- • Open charm • Forward/backward hadrons • Future interests

2. Au+Au: our key physics goals • Suppression/enhancement of J/Y yield in Au+Au relative to scaled p+p and d+Au • Extract open charm yield in Au+Au collisions to help disentangle J/Y suppression due to a (possible) QGP from nuclear medium effects • pion, kaon, heavy flavor production for non-zero rapidity • dN/dh, multiplicity, reaction plane from MVD (Multiplicity and Vertex Detector) All contribute to the goal of detecting and characterizing the quark-gluon plasma.

3. MVD history in words • The run-4 incarnation of the MVD is working. • The central barrel has been removed, at the request of PHENIX management, to reduce background for low mass e+e- measurements. • Delays in the production of Multi-chip modules (MCM’s), combined with poor yield, prevented us from installing the full detector until run-3 (~1/3 in run-1, ~2/3 in run-2). • Problems with the more conventional electronics (if you call anything with an optical fiber conventional) caused even bigger problems getting the data out. • LANL efforts (Sullivan, van Hecke, Hansen) with contributions from ORNL and Yonsei changed MVD from ~10% working in year-1 to >90% working today.

4. MVD history in pictures Current situation: Only pad detectors are installed (20% of total channels) Current version of the MVD: significant contributions to multiplicity, dN/dh, centrality, and reaction plane measurements. Potential to improve resolution in the muon arms – MVD: s(q)~0.3deg, s(f)~0.7; muon resolution at vertex: s(q)~0.7deg s(f)~1.6 deg. The acceptances only partially overlap (1.8<|h|<2.5 for MVD, 1.2<|h|<2.4 for muons). Can’t find the vertex.

5. MVD in Phenix run-2 (Au+Au) Landau fit for a single pad detector channel: s pedestal: 2.06 chan Most probable signal = 27.6 chan counts MVD-BBC vertex diff. ( cm): Good resol-ution, poor efficiency ADC channel In run-2, the partially installed/working MVD Vertex finding efficiency is ~38% for |z| < 32 cm. Would be ~100% for full MVD. counts

6. MVD – run 3 d+Au 2nd calibration step: more counts, pedestal subtracted, fit Landau 1st Calibration step: fit pedestal Landau fit counts counts ADC-pedestal Pedestal cut off ADC chan Noise levels acceptable in pad detectors. It is a hard problem – occupancy is only a few parts in 1000 – but we can do it.

7. Run 3 (d+Au) -- Correlation with other detectors • Raw hit multiplicity in MVD pad detectors has good correlation with BBC charge sum

8. Calculation of dN/dy correction factor Output = Pad detector “signal” + background output/input ~0.8 dN/dh Simulation input h h • Full simulation (Hijing) including detector and reconstruction • Background includes all particles which are not primary and loopers • The ratio of reconstructed to input accounts for both background and reconstruction efficiency • multiply measured data by ~0.8 to correct for background, etc.

9. d+Au: dNch/dh for Minimum Bias events • dNch/dhhas reasonable shape • Shaded bars represent uncertainty in the estimation of background • Needs more background study and normalization

10. Run4 – online monitoring plots BBC charge sum counts ADC chan MVD % occupancy The detector is working well in run 4. 30% 0 MVD % occupancy

11. Run-4 Muon arm performance We are trying to pull a J/Y signal out of the data. Alignment work is going on now, we are close to the needed resolution (s = 100 m), and should be able to reach it soon. Sample plot from alignment work: Radiograph of mTr hits: y -1 Dx 1mm x z

12. J/Y suppression? ``J/Y suppression by quark-gluon plasma formation,’’ Matsui and Satz 1986. predicts J/Y suppression by color screening. • Expected in Au+Au: • pA effects scaled up PLUS: • Hot hadron gas, comovers • QGP/dense matter modifications to production: • Debye screening, • Enhancement in coalescence models, balancing of D+D↔J/Y+X • Thermal production of charm • Energy loss and dead cone effect NA50

13. J/Y analysis The LANL team has led the muon arm effort for years, including the extensive work to extract the J/Y Signal from the p+p and d+Au data. North Arm dAu We will also be leaders in the effort to get the J/Y data out of the muon arms in run-4. This work has already begun. • 780 J/ψ’s • ~ 165 MeV counts 6 1 mass

14. R. L. Thews, M. Schroedter, J. Rafelski, Phys Rev C 63, 054905 Plasma Coalescence Model Binary Scaling Absorption (Nuclear + QGP) + final-state coalescence Absorption (Nuclear + QGP) L. Grandchamp, R. Rapp, Nucl Phys A709, 415; Phys Lett B 523, 60 J/Y in Au+Au collisions Here is what we have from Run-2 (J/Y -> e+e-): 13 counts in this plot, expect 1600 in each muon arm, 400 from central arm in run 4. The answer to this plot is Luminosity, Luminosity, and more Luminosity

15. Open charm production from single Leptons No statistically significant difference between scaled pp and dAu open charm yields at mid-rapidity. The Run-2 Au+Au data shows high pT suppression, but only at the ~1s level. Cocktail = p0 Dalitz + g conversions, etc Excess over cocktail = c+b: Electrons: central rapidity Forward y (muons): should show some suppression (if shadowing comes into play) – the relevant comparison to forward J/Y pT SIMULATED SPECTRA

16. Forward/backward hadrons PhenixPreliminary In d+Au, yields of light hadrons at forward and backward rapidities have been measured via their decays to muons. Mike talked about this. We plan to work on the same analysis in Au+Au. d+Au These measurements should allow us to measure high pT particle suppression at non-zero rapidity – an interesting extension of the exciting y=0 data.

17. Reaction plane Even with only the pad detectors, the MVD should be able to make good measurements of the reaction plane in AA collisions. Pad detectors ~25% more particles than BBC in ~47 times as many channels. (Whole MVD is x5 more particles). MVD and BBC acceptance do not generally overlap – so these augment current BBC capabilities. This gives another interesting way to look at jet suppression, J/Y suppression, open charm vs. the length of excited matter traversed.

18. Other future analysis efforts 1) Open charm from em coincidences (Hiroki Sato, soon to arrive postdoc). 2) The Y’ is has no feed-down from higher states. The Y’ gives a second probe for the study of charmonium suppression. Understanding this yield is also important for feed-down corrections for J/Y. Attempt to fit dAu data with J/Y + Y’ by D. Silvermyr, QM2004. Y’~3-5% of J/Y yield. Note: AuAu run-4 statistics expected to be slightly better than this. More AuAu data will probably be needed. dAu

19. Our future++ 3) Upsilon measurements. The Upsilon(1s) (b-bbar ground state) is not expected to be suppressed by color screening in a QGP. Measurements of Upsilon yields in p+p, p/d+Au, and Au+Au collisions would be a major addition to the PHENIX program. However, substantial increases in integrated luminosity are needed to study the Upsilon – for example the approximate number of Upsilons in run-4 will be around 0.5 per muon arm. More than an order of magnitude increase in integrated Luminosity will be needed. 4) Possible interest in LHC. Gerd Kunde had a previous involvement with ALICE EM calorimeter.

20. Summary • J/Y program in Au+Au collisions anxiously waiting for new run-4 data • Will do measurements of J/Y yield vs. reaction plane • Working to pull the J/Y signal out of Au+Au data • LANL initiated forward hadron analysis. • LANL key players in open charm measurements • MVD is doing reasonably well in Run-4 (part is not installed, but it could have gone in with acceptable noise)