LANL work on Au+Au data

• MVD past, present, future

• J/ +-

• Open charm• Forward/backward

hadrons• Future interests

Au+Au: our key physics goals• Suppression/enhancement of J/ yield in Au+Au

relative to scaled p+p and d+Au• Extract open charm yield in Au+Au collisions to

help disentangle J/ suppression due to a (possible) QGP from nuclear medium effects

• pion, kaon, heavy flavor production for non-zero rapidity

• dN/d, multiplicity, reaction plane from MVD (Multiplicity and Vertex Detector)

All contribute to the goal of detecting and characterizing the quark-gluon plasma.

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.

MVD history in pictures

Current version of the MVD: significant contributions to multiplicity, dN/d, centrality, and reaction plane measurements.

Potential to improve resolution in the muon arms – MVD: ()~0.3deg, ()~0.7; muon resolution at vertex: ()~0.7deg ()~1.6 deg. The acceptances only partially overlap (1.8<||<2.5 for MVD, 1.2<||<2.4 for muons).

Can’t find the vertex.

Current situation:Only pad detectors are installed (20% of total channels)

MVD in Phenix run-2 (Au+Au)

Landau fit for a single pad detector channel: pedestal: 2.06 chanMost probable signal = 27.6 chan

ADC channel

cou

nts

MVD-BBC vertex diff. ( cm): Good resol-ution, poorefficiencyco

un

tsIn run-2, the partially installed/working MVD Vertex finding efficiency is ~38% for |z| < 32 cm. Would be ~100% for full MVD.

MVD – run 3 d+Au

Noise levels acceptable in pad detectors. It is a hard problem – occupancy is only a few parts in 1000 – but we can do it.

Landau fit

Pedestal cut off

ADC-pedestalADC

chan

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1st Calibration step: fit pedestal

2nd calibration step: more counts, pedestal subtracted, fit Landau

Run 3 (d+Au) -- Correlation with other detectors

• Raw hit multiplicity in MVD pad detectors has good correlation with BBC charge sum

Calculation of dN/dy correction factor

● 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.

dN

/d

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tpu

t/in

pu

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~0.8

Simulationinput

Output =Pad detector“signal” +background

d+Au: dNch/d for Minimum Bias events

● dNch/d has reasonable shape● Shaded bars represent uncertainty in the

estimation of background● Needs more background study and normalization

Run4 – online monitoring plots

MVD % occupancy

MVD % occupancy

ADC chanBB

C c

harg

e

sum

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sThe detector is working wellin run 4.

0 30%

Run-4 Muon arm performanceWe are trying to pull a J/ signal out of the data.

Alignment work is going on now, we are close to the needed resolution ( = 100 ), and should be able to reach it soon.

-1 1mmx

Sample plot from alignment work:

Radiograph of Tr hits:

y

xz

J/ suppression?

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/+X•Thermal production of charm•Energy loss and dead cone effect

``J/ suppression by quark-gluon plasma formation,’’ Matsui and Satz 1986. predicts J/ suppression by color screening.

NA50

J/ analysis

North ArmdAu

780 J/ψ’s~ 165 MeV

The LANL team has led the muon arm effort for years, including the extensive work to extract the J/Signal from the p+p and d+Au data.

We will also be leaders in the effort to get the J/ data out of the muon arms in run-4. This work has already begun.

mass1 6

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J/ in Au+Au collisionsHere is what we have from Run-2 (J/ -> e+e-):

R. L. Thews, M. Schroedter, J. Rafelski, Phys Rev C 63, 054905Plasma 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

The answer to this plot is Luminosity, Luminosity, and more Luminosity

13 counts in this plot, expect1600 in each muon arm, 400 from central arm in run 4.

Open charm production from single Leptons

Cocktail = 0 Dalitz + conversions, etcExcess over cocktail = c+b:

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 ~1 level. Forward y (muons): should show some suppression (if shadowing comes into play) – the relevant comparison to forward J/

Electrons: central rapidity

pT

Forward/backward hadrons

Phenix Preliminary

d+Au

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.These measurements should allow us to

measure high pT particle suppression at non-zero rapidity – an interesting extension of the exciting y=0 data.

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/ suppression, open charm vs. the length of excited matter traversed.

Other future analysis efforts1) Open charm from e coincidences (Hiroki Sato, soon to arrive postdoc).

dAu

Attempt to fit dAu data with J/ + ’ by D. Silvermyr, QM2004. ’~3-5% of J/ yield. Note: AuAu run-4 statistics expected to be slightly better than this. More AuAu data will probably be needed.

2) The ’ is has no feed-down from higher states. The ’ gives a second probe for the study of charmonium suppression. Understanding this yield is also important for feed-down corrections for J/.

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.

Summary• J/ program in Au+Au collisions anxiously

waiting for new run-4 data• Will do measurements of J/ yield vs. reaction

plane• Working to pull the J/ 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)