Transcript Document

Workshop on Heavy Flavor Production
in High-Energy Nuclear Collisions
June 17-18, 2012
PHENIX Heavy Flavor Measurements in HI
Rachid Nouicer, BNL
 Charmonia Suppression in A+A Collisions
 Cold Nuclear Matter Effects
 Silicon Vertex Tracker: c and b Measurements
 Summary
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Why is Heavy Flavor Interesting?
Matsui and Satz, Plys. Lett. B 178 (1986) 416
Debye screening predicted to destroy J/y (1S: cc) in QGP with other sates
“melting” at different temperatures due to different sizes or binding energies.
Probe deeper into the medium: Energy loss of heavy quarks
• Dead-cone effect: gluon radiation suppressed at small angles (q < mQ/EQ)
Radiative energy loss
M. Djordjeevic et al.
Nucl. Phys. A733 (2004) 265
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S. Wicks et al. Nucl. Phys. A784 (2007) 426
Energy loss: Eg > ELQ > EHQ
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Motivation: why heavy flavor physics is so appealing?
One of the most surprising results from RHIC
R. Nouicer arXiv:0901.0910 [nucl-ex]
• Heavy flavor suppression
is as large as for light
quarks
• No dependence of energy
loss on flavor
• Do we understand the
energy loss mechanism?
• Where is Beauty
contribution?
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Motivation: why heavy flavor physics is so appealing?
One of the most surprising results from RHIC
R. Nouicer arXiv:0901.0910 [nucl-ex]
• Heavy flavor suppression
is as large as for light
quarks
• No dependence of energy
loss on flavor
• Do we understand the
energy loss mechanism?
• Where is Beauty
contribution?
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Motivation: Theoretical Calculations for HF
• Ralf F. Rapp, private communication
To be published by Ralf F. Rapp et al.
Realistic hydro (fit to multistrange and bulk particles) with heavy-quark diffusion
in the QGP, hadronization via resonance recombination/fragmentation, followed
by hadronic diffusion. There is no tuning of the HQ physics.
Nuclear modification factor
Elliptic flow
B+D-mesons via single electrons (NPE)
B+D-mesons via single electrons (NPE)
Ralf F. Rapp
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Motivation: Theoretical Predictions for HF
Nuclear modification factor
• Ralf F. Rapp, private communication
• D- and B-mesons via single electrons
(at mid-rapidity)
Ralf F. Rapp
Elliptic Flow
Ralf F. Rapp
Ralf F. Rapp
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Heavy Quarks as Probe of QGP
• p+p data:
→ baseline of heavy ion measurements
→ test of pQCD calculation: mc ~ 1.3 GeV, mb ~ 4.8 GeV >> Tc ,
ΛQCD  less affected than light quarks
• Due to their large mass heavy quarks are primarily produced by gluon fusion
in early stage of collision.
→production rates calculable by pQCD
• d+Au data:
- assess initial state effects
(M. Gyulassy and Z. Lin, PRC 51, 2177 (1995)
→cold nuclear matter effects
→Gluon shadowing, initial energy loss, Cronin effect
• Heavy ion data:
- they travel through the created medium interacting with its constituents
Studying energy loss of heavy quarks
→independent way to extract properties of the medium.
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Heavy Flavor Measurements
1) Direct: ideal but very challenging
- reconstruction of all decay products
Indirect measurement
e.g. D0  K- p+ (B.R.: 3.8 %)
Direct measurement
Charm: Mc ≈ 1.5 GeV
Bottom: Mb ≈ 4.75 GeV
2) Indirect (Alternative): heavy flavor semi leptonic decays contribute to
single lepton and lepton pair spectra
• Open heavy flavor
charm (and beauty) via electrons
c  e+ + anything (B.R.: 9.6%)
b  e+ + anything (B.R.: 10.9%)
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charm (and beauty) via muons
c  + + anything (B.R.: 9.5%)
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Measuring Heavy Flavor at PHENIX
Central Arms detect electrons
• |η| < 0.35 and 2 x /2 in azimuth
• pe > 0.2 GeV/c
• Electron identification:
- Ring Imaging Cerenkov detector
- Electromagnetic Calorimeter
• Silicon Vertex Tracker (VTX):
- new detector installed in 2011
- measure displaced vertices of
electrons at central rapidity to
separate c
e from b
e
→
e-
→
+
Forward Arms detect muons
• 1.2 < |η| < 2.4 and -2.2 < |η| < -1.2
• Muon Tracker reconstructs trajectories
and determines momentum
• Muon magnets and Muon Identifier
steel absorb hadrons, pion rejection
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e+
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Extraction of Heavy Flavor Signal
• Electron: measuring first inclusive electrons:
- Background subtracted method: using background cocktail composed of electron
sources measured at PHENIX: photonic and non-photonic sources:
 Conversion of photons from hadron decays in material
 Dalitz decays of light mesons (p0, h, w, h’, f)
 Ke3 : K±  p0 e± ne
 vector meson decays: r, w, f  e+ e heavy quarkonia decay
- Converter subtract method: adds material of known thickness around beam pipe,
measures conversion electrons by extra yield produced. Used at lower pT.
Both cocktail and converter methods agree
• Muon: measuring first inclusive muons:
- Background subtracted method: backround removed trough hadronic cocktail
subtraction. Backgrounds include:
- decay muons: resulting from light hadron decay.
- Punchtrough hadrons: hadrons that are not absorbed in steel absorber,
look identical to muons.
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Extraction of Heavy Flavor Signal
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Open Heavy Flavor (c,b) via
1) single electrons (at mid-rapidity)
2) single muons (at forward/backward rapidity)
e (or )
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Open Heavy Flavor Measurement in p + p Collisions
PRL 97, 252002 (2006)
Single electrons (|y| < 0.35)
PRD 76, 09002 (2007)
Single muons (1.4 < y < 1.9)
p+p
 Mid-rapidity, eHF yield is in agreement with pQCD (FONLL) calculations
 Forward rapidity, HF slightly higher that expected FONLL calculations
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Open Heavy Flavor Measurement in p + p Collisions
PRC 84, 044905 (2011)
Single electrons (|y| < 0.35)
PRD 76, 09002 (2007)
Single muons (1.4 < y < 1.9)
p+p
 Low pT HF lepton spectra is dominated by charm. So we simply extrapolate
to pT = 0 GeV/c using FONLL to get charm cross section
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Cross Section: Open Heavy Flavor in p + p Collisions
PHENIX: PRC
arXiv:1204.0754
d cc
dy
y 1.65
 0.139 0.029( stat )  0.051 ( sys) [m b]
0.058
d cc
dy
 0.123  0.098 ( stat )  0.365 ( sys ) [mb ]
y0
Agreement with FONLL within uncertainties.
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Total Open Charm Cross Section in p + p Collisions
Agreement with FONLL within uncertainties.
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Open Heavy Flavor (eHF) Measurement in Au+Au Collisions
PRL 98, 172301 (2007)
 Same method as in p + p
Nuclear modification factor
 Heavy flavor electrons from Au + Au
 Compared to Ncoll scaled p + p (FONLL x 1.71)
d 2 N AA / dpT dh
RAA ( pT ) 
TAAd 2 NN / dpT dh
<Nbinary>/inelp+p
(Nuclear Geometry)
RAA = 1 → no overall effect
RAA < 1 → suppression
RAA > 1 → enhancement
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Quantifying Medium Effects: eHF
Nuclear modification factor
 Heavy quarks suppressed
the same as light quarks,
and they flow, but less.
R. Nouicer arXiv:0901.0910 [nucl-ex]
 Suggests strong coupling of
heavy quarks to the medium
 Collective behavior is
apparent in eHF; but it is lower
than v2 of p0 for pT > 2 GeV/c.
 v2 results in Au+Au at √SNN =200 GeV
raised question about flow of heavy
quarks at lower beam energy.
 This contradicts models that
assumed only inelastic (radiative)
in-medium energy loss
 Separating D and B meson contributions key for establishing mass
hierarchy in understanding energy loss.
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Open Heavy Flavor eHF in d+Au system
 In peripheral d+Au collisions
production expected to be
similar to p+p. Consistent with
unity within uncertainties.
d
Au
d
 Central d+Au indicates slight
enhancement, similar to Cronin
effect in hadron production.
 Absence of CMN effects at
mid-rapidity in d+Au system.
 Large eHF suppression observed
in Au+Au collisions can safely be
attributed only to final state (hot
nuclear matter) effects.
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d
d
Au
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Open Heavy Flavor eHF
Energy Dependence of v2 (eHF):
Au+Au 200 and 62.4 GeV
Heavy quarks flow observed in Au+Au at lower energy as well
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Open Heavy Flavor eHF
System Size Dependence:
Au+Au vs Cu+Cu at 200 GeV
Comparison of central
Cu+Cu with semiperipheral Au+Au at
the same energy,
200 GeV, shows
good agreement.
Ncoll(CuCu) = 150
Npart(CuCu) = 86
Ncoll(AuAu) = 91
Npart(AuAu) = 62
No suppression is observed
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Open Heavy Flavor eHF
System Size Dependence:
Au+Au vs Cu+Cu vs d+Au at 200 GeV
Ncoll
Ncoll
RAA consistent across systems as a function of centrality
for d+Au, Cu+Cu and Au+Au
at the same energy, 200 GeV.
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Open Heavy Flavor in Cu+Cu at 200 GeV
Single electrons eHF vs single muons HF
Mid-rapidity vs forward rapidity
Suppression is stronger
at forward rapidity than
mid-rapidity- why ?
 Data in agreement with
I. Vitev’s prediction that
accounts for:
(1) for final state energy loss effects
with his dissociation model
(2) cold nuclear matter effects,
such as nuclear shadowing and
parton multiple scattering
Indication of Cold Nuclear Matter (CMN) effects
at forward rapidity in Cu+Cu system at 200 GeV
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The open charm spectra discussed in previous
slides serve as baseline for charmonium J/y
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Di-leptons in p+p at 200 GeV
Di-eHF: Midrapidity |y|<0.35
Di- HF: Forward Rapidity 1.2 < |y| <2.2
PHENIX has excellent capabilities of measuring different
quarkonia states in di-electron and di-muon channels.
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J/ψ Production at p+p at 200 GeV
arXiv: 1105.1966v1
PRL 98, 232002 (2007)
Total J/ψ cross-section : 181 +/- 22 nb (stat. + sys.)
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Closed Heavy Flavor in Au+Au at 200 GeV
Mid-rapidity (eHF) vs forward rapidity (HF)
Suppression is stronger at forward
rapidity than
mid-rapidity- why (CMN) ?
arXiv: 1103:6269
SPS: NA50, 17.2 GeV
Suppression in mid-rapidity is
comparable to that measured at SPS
energies.
No obvious pattern of the
suppression with energy density.
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What are the CNM effects that are contributing in J/y production?
J/y in d+Au  CNM thickness dependence
CNM effects appear to provide a
large fraction of the observed
suppression based on these
models.
Reasonable agreement with EPS90
model for central but not peripheral
d
Au
eHF : |y| <0.35
HF : |y|
CGC calculations
can’t reproduce mid-rapidity
(Nucl. Phys. A 770(2006) 40).
EPS90 with linear thickness
dependence fails to describe
centrality dependence of forward
rapidity region.
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Closed Heavy Flavor in Au+Au at 200 GeV
What about v2 of J/y?
Forward rapidity v2(HF): J/y
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What Next?
Nuclear modification factor
B+D-mesons via single electrons (NPE)
 Separating D and B meson
contributions key for
establishing mass hierarchy in
understanding energy loss…
Ralf F. Rapp
D  eHF + X and B  eHF + X
Elliptic Flow
Ralf F. Rapp
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Nuclear modification factor
Ralf F. Rapp
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D  eHF and B  eHF with PHENIX Silicon Vertex Tracker (VTX)
Installed in 2010
data in Run-11 and 12
To understand these medium effects in
more detail it is imperative to directly
measure the nuclear modification and
flow of D- and B-mesons
independently (c  eHF and b  eHF).
Barrel 4
Barrel 3
Barrel 2
Barrel 1
p
Barrel 1
Barrel 2
Barrel 3
Barrel 4
e
D
DCA
B
Life time (ct)
D0 : 123 mm
B0 : 464 mm
p
e
Layer 4
Layer 3
Layer 2
Layer 1
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Technology Choices: Silicon Pixel Barrels 1 & 2
ALICE1LHCb readout chip:
Pixel:
50 µm (f) x 425 µm (Z).
Channels: 256 x 32.
Output: binary, read-out in
25.6 s@10MHz.
Radiation Hardness: ~ 30 Mrad
Sensor module:
4 ALICE1LHCb readout chips.
Bump-bonded (VTT) to silicon sensor.
Thickness: 200 m
Thickness: r/o chips 150 µm
Active area
r
1.28 cm = 50mm x 256
z
1.36 cm = 425mm x 32
Solder bump
~20m
Half-ladder (2 sensor modules + bus)
1.36 cm x 10.9 cm.
Thickness bus: < 240 µm.
SPIRO module
Control/read-out a half ladder
Send the data to FEM
FEM (interface to PHENIX DAQ)
Read/control two SPIROs
Interface to PHENIX DAQ
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Technology Choices: Silicon Pixel Barrels 1 & 2
• Sensor module consists of 4 ALICE Pixel readout chips
bump-bonded to silicon sensor
• One readout unit, half stave, made from two sensor modules
• Half stave is mounted on the support structure
• Pixel BUS to bring data out and send control
signal into the readout chip is mounted on the
half stave
• Each detector module is built of two half
staves, read out on the barrel ends
Pixel BUS
Half stave
Full stave
Sensor
Sensor
Sensor
Module
Bus
Glue
Sensor
Readout chip
Glue
Stave
Data
1.4cm
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Thermo plate +ALICE
cooling
22cmNouicer
LHCB1
chip - BNL
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Technology Choices: Silicon Stripixel Barrels 3 & 4
•
•
•
“New technology: unique to PHENIX”
Innovative design by BNL Instr. Div. : Z. Li et al., NIM A518, 738 (2004);
R. Nouicer et al., NIM B261, 1067 (2007);
R. Nouicer et al., Journal of Instrumentation, 4, P04011 (2009)
• DC-Coupled silicon sensor
• Sensor single-sided
• 2-dimensional position
sensitivity by charge sharing
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Technology Choices: Silicon Stripixel Barrels 3 & 4
 Sensors produced by HPK with thickness of 625 μm
 Point-symmetric structure of readout lines wrt the center of the sensor
 Readout pads in longer edges for




ladder structure design
No dead space in the middle
Sensor size : 3.4×6.4 cm2
Pixel array : 80×1000 μm2 pitch
# readout strip
o x-strip : 128×3×2
o u-strip : 128×3×2
o Total : 1536 channels/sensor
 Current per strip: 0.12 nA
 Note: Stripixel sensor technology,
including the mask design and
processing technology has
transferred from BNL to HPK.
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Technology Choices: Silicon Stripixel Barrels 3 & 4
 Sensors produced by HPK with thickness of 625 μm
 Point-symmetric structure of readout lines wrt the center of the sensor
 Readout pads in longer edges for




ladder structure design
No dead space in the middle
Sensor size : 3.4×6.4 cm2
Pixel array : 80×1000 μm2 pitch
# readout strip
o x-strip : 128×3×2
o u-strip : 128×3×2
o Total : 1536 channels/sensor
 Current per strip: 0.12 nA
 Note: Stripixel sensor technology,
including the mask design and
processing technology has
transferred from BNL to HPK.
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Stripixel Ladders Mass Production at BNL
Dow Corning glue: 100 [um]
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Placing modules on stave
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Laser scan of
the stave (flatness)
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Stripixel Barrels Assembly and Testing at the Lab.
WEST: Layer 3 (Stripixel): 8 ladders
EAST: Layer 3 (Stripixel): 8 ladders
EAST: Layer 4 (Stripixel): 12 ladders
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WEST: Layer 4 (Stripixel): 12 ladders
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Pixel Barrels Assembly and Testing at the Lab.
Layer 1 (PIXEL): 5x2 ladders
Layer 2 (PIXEL): 10x2 ladders
Spiro Board
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Stripixel: Readout Chain
Detector at the IR
Stripixel
ladders
at IR
Stripixel DIB in the rack room DCMII: Zero-Suppression
Optical
cables
75 meters
at DIB stage Pedestal Correction:
VTX-Stripixel: Run-11: p+p at 500 GeV
M1
M2
p+p at 500 GeV
M3
Data Transfer
DIB to DCM2
M4
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Stripixel: Performance Results
• Raw hits data from p+p at 500 GeV Beam Data in Stripixel
Pedestal correction and zero suppression are working properly
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Stripixel: Performance Results
p+p at 500 GeV
Multiplicity Distribution
(uncorrected)
f
• Acceptance of hits distribution
(can be used to build reaction plan)
h
h
• These basic measurements (multiplicity, flow…) with the VTX
are the first step towards a new era of heavy flavor discoveries
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VTX at RHIC Run-11: Display of Single Event
1) VTX RUN-11: p+p at 500 GeV
3) VTX RUN-11: Au+Au at 200 GeV
2) VTX RUN-11: Au+Au at 19.6 GeV
4) VTX RUN-11: Au+Au at 27 GeV
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PHENIX-VTX at RHIC: Display of Single Event
VTX RUN-12: p+p at 200 GeV
Primary Vertex: BBC vs VTX
VTX RUN-11: Au+Au at 200 GeV
Primary vertex
single event
Data: AuAu
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Beam size
Data: AuAu at 200 GeV
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DC Based Tracking with VTX Cluster (DCTVC)
• Response of the EMCal Detector
E/p distribution with enabling Rich detector “n ”
0
h-
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Run-11 data:
Au+Au at 200 GeV
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Performance Plot: Extracting b and c Signals
Electron DCA vs Charged Hadron DCA
L , Ks
 DCA distributions of electrons are
broader than that of all charged
 The difference can be due to heavy
flavor signal
 Large DCA tail: Can it be b-signal?
 Needs comparison with expected
shape from MC
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Picture Taken on November 22nd, 2011
FVTX has been built and integrated with VTX
VTX
FVTX
7/7/2015
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[email protected]
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Picture Taken on November 22nd, 2011
VTX and FVTX installed and took data in Run-12
east
west
7/7/2015
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[email protected]
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Summary
 In p+p collisions, eHF yields have been measured and agree with pQCD
calculations (FONLL)
 Open Heavy Flavor shows medium effects similar to those light
hadrons in central Au+Au collisions
 Initial states effects do not appear to explain eHF suppression in Au+ Au
 consistent with creation of a very dense and strongly interacting
deconfined medium
 However, initial state effects apparent at forward rapidity
 Recent Cu+Cu and d+Au measurements indicate additional sizable cold
nuclear matter effects in different kinematic regions.
 New PHENIX-VTX detector open new era to make precise
measurements of open heavy Flavor: separating D and B meson
contributions key for establishing mass hierarchy in understanding
energy loss…
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