PHENIX Heavy Flavor Measurements in the RHIC II Era
Vince CiancioloRHIC II Heavy Flavor Workshop
April 28, 2005
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Outline
• Why are we interested in heavy flavor?• PHENIX upgrades• RHIC II luminosity guidance• Into an era of precision heavy-flavor
measurements at RHIC…
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Generic Advantages of Hard Probes
• Produced early– Sample medium
• Scale w/ Nbinary (in the absence of medium effects)– pp reactions calibrate
probes, allowing detection of medium effects, test pQCD
q: fast color triplet
g: fast color octet
Q: slow color triplet
QQbar: slow color singlet/octet
Virtual photon: colorless
Real photon: colorless
Unknown Medium
Inducedgluon radiation?
EnergyLoss?
Dissociation?
Controls
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• Initial gluon density, shadowing– Dominance of gluon fusion production mechanism
• Gluon spin structure function• Interaction of slow heavy quarks in the medium
– Less energy loss than light quarks?– Participation in flow?
• Test for additional thermal production• Onium production mechanism, suppression
pattern• Backgrounds for other interesting signals
– Drell-Yan, thermal di-leptons
What would we like to know that heavy flavor measurements can tell us
about?
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What can we measure?• Open heavy flavor (HF)
– y, pT dependence– Centrality dependence– Reaction plane dependence– Tagged HF jets– HF di-lepton correlations
• J/ – y, pT dependence– Centrality dependence– Reaction plane dependence– J/ - hadron correlations– Polarization ’, c and B contributions – Compare to ’,
• Everything should be studied vs. √s, collision species.
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What have we measured (or collected data for)?
• Open heavy flavor (HF)– y, pT dependence e
– Centrality dependence e
– Reaction plane dependence e
– Tagged HF jets No– HF di-lepton correlations No
• J/ – y, pT dependence e
– Reaction plane dependence No– J/ - hadron correlations No– Polarization No ’, c and B contributions No – Compare to ’, No
• Everything should be studied vs. √s, collision species. e
e – Good start on exploratory measurementsc : 0.8 < pT (GeV/c) < 2.5
c+b : pT (GeV/c) < 4.5Species : dAu, pp, CuCu, AuAu
√s : 200 GeVStatistics : More is always better (allows reduction in statistical and systematic
errors)
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Silicon Vertex Detector • Four barrel layers
– Two ALICE pixel bus layers– Two strip-pixel layers
• Four end-cap pixel layers• Displaced vertex (σ ~50 m)• Full azimuthal inner tracking
|η| < ~2.4– Improve acceptance for -jet
correlations, D K• Connect to tracks in central
and muon arms– Tag heavy flavor decays
• c,b e,• B J/
– Improve onium resolution– Eliminate decay hadrons– Reduce high-pT background
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Nose Cone Calorimeter
• Replace central arm magnet nosecones (Cu) w/ tungsten-silicon calorimeters
• Coverage at forward/backward rapidity: 0.9 < |η| < 3.5 /0 separation for pT < 30
GeV/c – Jet identification
identification gives good acceptance for c J/ +
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Muon Trigger Upgrade• Three layers of RPCs with 2D
(θ,φ) pad readout• Provides online momentum
measurement to improve Level-1 trigger rejection– Single-particle
• pT cut• W spin-measurements in pp
– Two-particle • Minv cut• onium measurements in AA
– Necessary to take complete advantage of luminosity upgrades
• Provides improved high-multiplicity background rejection
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Disclaimer
• Be wary of Hypothetical Future Value predictions…
• As always, the Devil is in the details.
When rate estimates look too good to be true they probably are.
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RHIC II Luminosity – CAD Guidance
x 35 increase for ppx 10 increase for CuCu
x 15 increase for dAux 15 increase for AuAu
http://rhicii-heavy.bnl.gov/doc/RHIC_II_Luminosity_Roser.xls
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RHIC II Yields – ADF, MJL Guidance
• Assume CAD “Maximum Average” Luminosity Projection, 12 week runs, known PHENIX uptime (60%) to get Live Delivered Luminosity.
• Use measured values when possible to calculate pp σ’s, B.R.’s.• Assume nuclear scaling - (AB), w/=1 for , =0.92 for others.• Use stated RF efficiency, diamond size to get vertex cut efficiency.• Use measured PHENIX performance, assume PHENIX SiVTX, Nosecone
Calorimeter, Muon Trigger upgrades to get acceptances, efficiencies.
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Onium Yields
• Precision measurements of the J/• Exploratory measurements of the other onium states.• Steep increase at √s = 500 GeV illustrates the significant
difficulties for measurements at lower energies.
Signal/System pp (200 GeV) pp (500 GeV)CuCu (200
GeV) AuAu (200 GeV) dAu (200 GeV)
J/ee 55,054 609,128 73,921 44,614 29,919
′(2S)ee 993 10,985 1,333 805 540
_c0+J/ee 100 2,578 134 81 54
_c1+J/ee 1,340 40,870 1,800 1,086 728
_c2+J/ee 2,190 59,296 2,941 1,775 1,190
(0,1,2)ee 210 3,032 547 397 184
BJ/ee 1,237 41,480 4,567 3,572 1,085
J/ 468,741 5,483,006 653,715 394,535 258,136
′(2S) 8,453 98,880 11,789 7,115 4,655
_c0+J/ 3,822 99,824 5,330 3,217 2,105
_c1+J/ 51,215 1,582,561 71,425 43,107 28,204
_c2+J/ 83,702 2,296,069 116,732 70,451 46,095
(0,1,2) 528 7,723 1,429 1,035 469
BJ/ 2079 76466 5756 3752 1824
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Other Yields
• From similar estimates in SiVTX proposal:– D K : 1000 counts (S/B ~ 3%) for
central AuAu pT
> 2 GeV/c
– cc e or : pT < 7 GeV/c
– bb e or : pT < 8 GeV/c
• From CDR estimates scaled by onium yield expectations then and now– cc , cc ee, cc e : Minv < 8
GeV/c
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Measuring Open Heavy Flavor in PHENIX
• Measurement of open heavy flavor in PHENIX is based on the semi-leptonic decay modes of B and D mesons.
• Other contributions to inclusive lepton spectra are determined and subtracted; remainder attributed to heavy flavor decays.
c c
0DK
0D
K-
+
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Measuring Heavy Flavor (y=0) in PHENIX Cocktail Method
Inclusive electron spectrum in AuAu @ 200 GeV/c
• Many sources contribute to inclusive electron spectrum.
• Dominant contribution from 0’s (via Dalitz decay and conversion).
• These are very well measured by PHENIX in the same apparatus.
• S/B decreases w/ increasing pT.
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Measuring Heavy Flavor (y=0) in PHENIX Converter Method
• At low-pT we directly measure dominant -conversion backgrounds by inserting an extra converter of known thickness.
• Dalitz contribution follows deterministically.• Statistics-limited at high-pT (rely on cocktail, OK since S/B
higher).
Non-
/ e
lect
ron r
ati
o
For pT > 0.8 GeV/c S/B > 0.4
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Note: Bottom dominates for pT> 2.5 GeV/c
• Comparison with PYTHIA (tuned to available data)– pT < 1.5 GeV/c: reasonable
– pT > 1.5 GeV/c: spectra “harder” than PYTHIA LO
• hard fragmentation?• bottom enhancement?• higher order contributions?
pp Results
• Comparison with FONLL– Fixed Order Next-to-Leading Log
pQCD calculation (M. Cacciari, P. Nason, R. Vogt hep-ph/0502203)
– better description of spectral shape
– still room for further contributions• from jet fragmentation?
PHENIX data
consistent with STAR (PRL 94,
062301 (2005)) within errors!
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Total Charm Yield Nbinary• Background-subtracted “heavy-
flavor” e± pT spectra vs. centrality w/ converter analysis
• Insufficient statistics at pT > 1.5 GeV/c to study modification of spectral shape
Total yield for pT > 0.8 GeV/c
• Total charm yield in AuAu agrees with binary scaled pp yield (as expected for point-like pQCD process)!
PHENIX: PRL 94, 082301 (2005)
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Charm May Flow• PHENIX HF electron spectra @ 130 GeV/c are compatible w/
no interactions and also with hydrodynamics.• Measure flow, go to higher pT
Batsouli et al., Phys. Lett. B557, 26
S.S. Adler et al., nucl-ex/0502009
Theoretical predictions from Greco et al., Phys. Lett. B595, 202
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Charm RAA(pT) 1
• Need to go to cocktail analysis to obtain sufficient statistics at high-pT.• Will lower systematics at low-pT by combining with converter method.
ppAA
AAAA dT
dNR
PHENIX Preliminary
RAA with yield above 2.5 GeV/c
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Measuring Heavy Flavor at Forward Rapidity in the PHENIX Muon Arms
Z (cm)400 120
Final Decay
Muon flux
Total flux
I I hadron
Gap 0 1 2 3 4
II decay muon
log I
I (
part
icle
flux)
Reconstructed to gap4
I3I3inclusive
I3I3exclusive
Hadron punch-through
absorber
II prompt muon
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Measuring Heavy Flavor at Forward Rapidity in the PHENIX Muon Arms
• Extract decay component from z-vertex slope of normalized muon yield.• Calculate punchthrough component with simplified absorption model:
• Cocktail input not well-measured as in central-arm measurement.• Absorber thick, any error in strong interaction description amplified by ~e10.• At low (high)-pT systematics dominated by decays (punchthroughs, competing c/b production)
Prompt muons
Punch-through hadrons
Decay muons
PHENIX PRELIMINARY
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Expected D K statistical significance (S/√B) for different DCA cuts (pT > 2 GeV/c, 200M AuAu min. bias. events)
Synergistic Benefits of Detector/Luminosity Upgrades for Open Heavy Flavor Measurement
• Detector upgrades assist by determining decay vertex.– Allows direct measurement of
charm via D K– Reduces backgrounds at low-pT
– Allows statistical separation of c/b at high-pT
– Allows direct elimination of hadron decay muons.
• Luminosity upgrades extend pT reach and allow reduction of systematic errors.– Additional special runs (e.g., w/ different converter thicknesses and
locations, different field configurations, etc.)– Finer binning of DCA dependence for c/b separation.– Better determination of punchthrough absorption.
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J/ in pp
In pp we’ve measured the J/ close to pT = 0 and over much of the rapidity range.
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J/ in dAu
Modest cold nuclear effects seen, but data are not sufficient to completely understand those effects.
dA/ pp = (2A)
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Coalescence model (Thews et al)
y = 1.0
y = 4.0Stat. Model (Andronic et al.)
Absorption model (Grandchamp et al.)
Phys.Rev.C69, 014901,2004
J/ in AuAu
• Low-statistics measurement in central arm from Run-2. • Much larger data sets in central and muon arms from Run-4
are currently in production.
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J/ in CuCu
• We’re just getting started, but we have nice mass peaks from near-line analysis of LVL2-filtered data.
central arm north muon arm
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Synergistic Benefits of Detector/Luminosity Upgrades for
Onium Measurements• Statistics, statistics, statistics
– Higher pT coverage– More centrality bins– More systems, energies– Triggering improvements needed
for Level-1 di-muon triggering in ion collisions w/ RHIC II luminosity
– Polarization ′ and
• Background elimination– J/ background dominated by
hadron decays which can be largely eliminated w/ silicon detector.
• Resolution– Especially important for ′ and ’s
• Feeddown c J/ + (NC Calorimeter)– B J/ + X (Forward Silicon)
=1.0-1.5
Minv() – Minv()
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Other HF Topics• cc e+e-
– Drell-Yan– IM di-leptons
• Gluon structure function• Charm-jet tomography
– Tag charm jet w/ electrons– Measure J/ near- and far-
side correlations
R. Rapp, nucl-th/0204003
e pT : 3 – 4 GeVe pT : 3 – 4 GeVe pT : 3 – 4 GeVe pT : 3 – 4 GeVe pT : 3 – 4 GeVe pT : 3 – 4 GeVe pT : 3 – 4 GeVe pT : 3 – 4 GeVe pT : 3 – 4 GeVe pT : 3 – 4 GeVe pT : 3 – 4 GeVe pT : 3 – 4 GeVe pT : 3 – 4 GeVe pT : 3 – 4 GeVe pT : 3 – 4 GeVe pT : 3 – 4 GeVe pT : 3 – 4 GeVe pT : 3 – 4 GeVe pT : 3 – 4 GeVe pT : 2 – 3 GeVe pT : 2 – 3 GeVe pT : 2 – 3 GeVe pT : 2 – 3 GeVe pT : 2 – 3 GeVe pT : 2 – 3 GeVe pT : 2 – 3 GeVe pT : 2 – 3 GeVe pT : 2 – 3 GeVe pT : 2 – 3 GeVe pT : 2 – 3 GeVe pT : 2 – 3 GeVe pT : 2 – 3 GeVe pT : 2 – 3 GeVe pT : 2 – 3 GeVe pT : 2 – 3 GeVe pT : 2 – 3 GeVe pT : 2 – 3 GeVe pT : 2 – 3 GeVe pT : 1.5 – 2 GeVe pT : 1.5 – 2 GeVe pT : 1.5 – 2 GeVe pT : 1.5 – 2 GeVe pT : 1.5 – 2 GeVe pT : 1.5 – 2 GeVe pT : 1.5 – 2 GeVe pT : 1.5 – 2 GeVe pT : 1.5 – 2 GeVe pT : 1.5 – 2 GeVe pT : 1.5 – 2 GeVe pT : 1.5 – 2 GeVe pT : 1.5 – 2 GeVe pT : 1.5 – 2 GeVe pT : 1.5 – 2 GeVe pT : 1.5 – 2 GeVe pT : 1.5 – 2 GeVe pT : 1.5 – 2 GeVe pT : 1.5 – 2 GeV
PRELIMINARY PRELIMINARY PRELIMINARY
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Conclusions• There’s a famous Indian fable about six blind men
who come to very different conclusions about the form of an elephant due to their limited examinations.
• With detector upgrades and RHIC II luminosities we can truly embark on precision heavy flavor measurements of sQGP (or whatever we choose to call the stuff we’ve made) and come to a better understanding of its full nature.
Wall?Fan?
Snake?
Spear?Rope?
Tree?
…Moral:
So oft in theologic wars, The disputants, I ween, Rail on in utter ignorance Of what each other mean, And prate about an Elephant Not one of them has seen!
John Godfrey Saxe (1816-1887)
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• Backup slides
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Silicon Vertex Detector – Details2D single-sided detectors for outer barrels
Modified BTeV chip for end cap readout
ALICE pixel bus for inner barrels
Vital stats
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Silicon Vertex Detector - Coverage• Complete coverage of central arms• Nearly complete coverage of muon arms
– Two small regions w/ only two hit Si planes• Essentially 4 tracking for |η| < ~2.4
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Nosecone Calorimeter – DetailsNot This Talk
e/m compartments Hadronic (leakage)
00// identifier identifier(strip-pixels)(strip-pixels)
downstream
Si Si padspads
tungstentungsten
upstream
Single layer of stripPixels
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Muon Trigger Upgrade – Detailsscintillator HVRPC
Time resolution ~ 3.5 ns
Efficiency for cosmics
Raw signals