LANL work on Au+Au data. MVD past, present, future J/ Y -> m + m - Open charm Forward/backward hadrons Future interests. Au+Au: our key physics goals. Suppression/enhancement of J/ Y yield in Au+Au relative to scaled p+p and d+Au
All contribute to the goal of detecting and characterizing the quark-gluon plasma.
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.
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
MVD-BBC vertex diff.
Good resol-ution, poor
In run-2, the partially installed/working MVD Vertex finding efficiency is ~38% for |z| < 32 cm. Would be ~100% for full MVD.
2nd calibration step: more counts, pedestal subtracted, fit Landau
1st Calibration step: fit pedestal
Pedestal cut off
Noise levels acceptable in pad detectors. It is a hard problem – occupancy is only a few parts in 1000 – but we can do it.
BBC charge sum
MVD % occupancy
The detector is working well
in run 4.
MVD % occupancy
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:
``J/Y suppression by quark-gluon plasma formation,’’ Matsui and Satz 1986. predicts J/Y suppression by color screening.
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.
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.
R. L. Thews, M. Schroedter, J. Rafelski, Phys Rev C 63, 054905
Plasma Coalescence Model
Absorption (Nuclear + QGP) + final-state coalescence
Absorption (Nuclear + QGP)
L. Grandchamp, R. Rapp, Nucl Phys A709, 415; Phys Lett B 523, 60
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
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
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.
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.
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.
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.