j/psi production in au+au and cu+cu collisions at rhic-phenix susumu oda (doctor course student)...
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J/psi production in J/psi production in Au+Au and Cu+Cu Au+Au and Cu+Cu collisions at RHIC-collisions at RHIC-PHENIXPHENIX
J/psi production in J/psi production in Au+Au and Cu+Cu Au+Au and Cu+Cu collisions at RHIC-collisions at RHIC-PHENIXPHENIXSusumu Oda (Doctor course Susumu Oda (Doctor course student)student)Hamagaki group, CNS, University Hamagaki group, CNS, University of Tokyoof Tokyo
2007/08/282007/08/28CISS07, Student/post-doc sessionCISS07, Student/post-doc session
Susumu Oda (Doctor course Susumu Oda (Doctor course student)student)Hamagaki group, CNS, University Hamagaki group, CNS, University of Tokyoof Tokyo
2007/08/282007/08/28CISS07, Student/post-doc sessionCISS07, Student/post-doc session
1/111/11
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My interest is …Create QGP (Quark Gluon
Plasma) and study its property experimentally.
A theoretical view of QGP will be given in Dr. Hirano’s lecture (Thu. afternoon).
QGP is a state in which quarks and gluons are deconfined.
In ordinal matter, quarks and gluons are confined.
We cannot extract single quark nor single gluon from the matter.
This state might exist in early universe.
QGP may be created in high temperature and high density circumstances. 2/112/11
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How do we create such high temperature and density environment?
Collides heavy ion with extremely high energy (about 100A GeV + 100A GeV=200 GeV per nucleon-pair in C.M.S.).
197Au, 63Cu, 208Pb, …We’re only interested in only mass
number A. We don’t care about those nuclear
structure. BNL-AGS, CERN-SPS (1980s-) : ~ 4-17
GeV/nucleon-pair BNL-RHIC (USA) (2000-) : 200 GeV/nucleon-
pairCERN-LHC (Switzerland) (2008-) : 5.5
TeV/nucleon-pair
3/113/11
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Our group …
Participates in the PHENIX experiment at BNL-RHIC (circumference=3.8km). Starts to participate in ALICE
experiment at CERN-LHC (27km). These facilities are very very large
to collide particles with very high energy.
4/114/11
高原TakaharaLHC
This is me
He is our boss
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What are the signals of QGP?How can we know whether QGP is created or not? Really big problem.
No definitive conclusion.
But, one good candidate is J/psi. J/psi is a bound state of a charm quark and an
anti-charm quark.J/psi will be created by only initial collisions. J/psi would melt and disappear in hot QGP. Yield would be suppressed. If J/psi melt in QGP, we detect the less number of
J/psi’s than expected.
I study J/psi production in Cu+Cu collisions.
5/115/11
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How do we measure J/psi?
J/psi has lepton-pair decay channels.
Branching ratio (J/psie+e-)=5.94%, (J/psi+-)=5.93%
Electron (Cherenkov light, electromagnetic interaction) and muon (less absorption cross section by material) are easily identified.
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Cherenkov light ring
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PHENIX detector is …
7/117/11
Vertex, centralityTiming, charged particle multiplicity
BBC
Spectator neutronZDC
Forward rapidity (1.2<|y|<2.2, +- pair)
TrackingMWPC
PIDDrift tube, absorber
Mid rapidity (|y|<0.35, e+e- pair)
TrackingDC, MWPC
PIDRICH, EMCal
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J/psi peaks at 3.097GeV/c2 in Cu+Cu
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Invariant mass of e+e-
Background subtraction Unlike sign pair (e+e-) – Like sign pair (e+e+, e-e-)
Mass(ee) (GeV/c2)
Counts (0.01GeV/c2)-1
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Ratio of measured yield to expected yield : RAA
If there is no hot nuclear effect nor cold nuclear effect, a heavy ion collision can be understood as superposition of nucleon-nucleon collisions (p+p, p+n, n+n). p+p : No nuclear effectp(d)+A : cold nuclear effect
Hot region is limited and is soon cooled down. A+A : hot nuclear effect (QGP) + cold nuclear effect
Large hot region isn’t soon cooled down. We can know hot nuclear effect by
(A+A)/(p+p)-(d+A)/(p+p) (hot+cold)-cold = hot nuclear effect
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ppcoll
AAAA YieldN
YieldR
p+p d+A A+A
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RAA vs Npart (the number of participating nucleon)
J/psi seems to be melted and QGP seems to be created at RHIC.
10/1110/11
absorption0 mb
3 mb
Red : Au+Au |y|<0.35Magenta : Cu+Cu |y|<0.35Blue : Au+Au 1.2<|y|<2.2Aqua : Cu+Cu 1.2<|y|<2.2
peripheral central
no nuclear effectno nuclear effect
cold nuclear effectcold nuclear effectfrom d+Au datafrom d+Au data
HotHot and cold and cold nuclear nuclear effectseffects
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J/psi seems to be melted and QGP seems to be created. However, …
Our knowledge on cold nuclear matter is limited.
More d+A (or p+A) data is needed.
There is feed down from excited states.
We need to measure those excited states, but it is difficult measure them.
Regeneration from uncorrelated charm.
Statistics of J/psi data at RHIC is limited by its small production cross section. At LHC energy (RHIC energy x28)
J/psi cross section is much larger and we can collect larger data samples. With the large data samples, we can
study the property of QGP. 11/1111/11
J/c
c-bar c
0 mb
3 mb
deuteron gold