star decadal plan 1 carl gagliardi texas a&m university
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STAR Decadal Plan 1
STAR Decadal Plan
Carl GagliardiTexas A&M University
STAR Decadal Plan 2
The charge• A brief summary of the detector upgrades already (or soon to be)
in progress … This can even be summarized in tabular form, and should be consistent with the latest RHIC Midterm Plan.
• The compelling science goals you foresee for RHIC A+A, p+p, and d+A collisions that can only be carried out with additional upgrades (or replacements) of detector subsystems or machine capabilities (e.g., further luminosity or diamond size improvements).
• Prioritized, or at least time-ordered, lists of the major (above $2M total project cost) and more modest (below $2M total project cost) new detector upgrades
• Any plans or interest your Collaboration has in adapting your detector or detector subsystems (or detector R&D) to study electron-nucleon and electron-ion collisions with an eventual eRHIC upgrade.
• The envisioned evolution of your Collaboration through the decade
STAR Decadal Plan 3
Remarkable discoveries at RHICThe first six years
• A+A collisions– Jet quenching– Perfect liquid– Number of constituent quark scaling– Heavy-quark suppression
• Polarized p+p collisions– Large transverse spin asymmetries in the pQCD regime
• d+A collisions– Possible indications of gluon saturation at small x
STAR Decadal Plan 4
The discoveries continue
• A+A collisions– First ever observation of an anti-hypernucleus– Azimuthal charged-particle correlations that may arise from local
strong parity violation– Even b-quark production is suppressed in central Au+Au
collisions
• Polarized p+p collisions– Most precise constraints to date on the polarization of the gluons
• Global analysis that combines DIS, SIDIS, and RHIC data• Contribution to proton spin from gluons with 0.05 < x < 0.2 is small
• d+A collisions– Dramatic broadening of forward π0-π0 correlations in central d+Au
• Clearest indication to date that the onset of gluon saturation is accessible at RHIC
STAR Decadal Plan 5
New research areas
• STAR and RHIC continue to perform very well under extreme conditions– Au+Au collisions at 7.7 GeV
– Charge-sign separation to pT ~ 50 GeV
STAR Decadal Plan 6
Key unanswered questions
• What is the nature of QCD matter at the extremes?– What are the properties of the strongly-coupled system
produced at RHIC, and how does it thermalize?– Where is the QCD critical point and the associated first-order
phase transition line?– Are the interactions of energetic partons with QCD matter
characterized by weak or strong coupling? What is the detailed mechanism for partonic energy loss?
– Can we strengthen current evidence for novel symmetries in QCD matter and open new avenues?
– What other exotic particles are produced at RHIC?
• What is the partonic structure of nucleons and nuclei?– What is the partonic spin structure of the proton?– What are the dynamical origins of spin-dependent interactions in
hadronic collisions?– What is the nature of the initial state in nuclear collisions?
STAR Decadal Plan 7
Tracking: TPC Particle ID: TOF
Full azimuthal particle identification over a broad range in pseudorapidity
STAR: a beautiful detector
Recent upgrades:DAQ1000TOF
have already begun to position STAR for the coming decade
Electromagnetic Calorimetry:
BEMC+EEMC+FMS(-1 ≤ ≤ 4)
STAR Decadal Plan 8
How to answer these questions• Hot QCD matter: high luminosity RHIC II (fb-1 equivalent)
– Heavy Flavor Tracker: precision charm and beauty– Muon Telescope Detector: e+μ and μ+μ at mid-rapidity– Trigger and DAQ upgrades to make full use of luminosity
• Phase structure of QCD matter: energy scan– Electron cooling if lowest beam energies most promising
• Near-term upgrades for p+p collisions– Forward GEM Tracker: flavor-separated anti-quark polarizations– Forward Hadron Calorimeter: strange quark polarization– Roman Pots phase II: search for glueballs
• Nucleon spin and cold QCD matter: high precision p+p and p+A, followed by e+p and e+A– Major upgrade of capabilities in forward direction– Devote the beam time needed to do p+A, rather than d+A– Existing mid-rapidity detectors well suited for portions of the
initial e+p and e+A program
STAR Decadal Plan 9
Tracking: TPC
Forward Gem Tracker(2011)
Particle ID: TOF
Full azimuthal particle identification over a broad range in pseudorapidity
Evolution of STAR
Additionalupgrades:Muon Telescope
Detector Trigger and DAQForward Upgrades
Heavy Flavor Tracker (2013)
Electromagnetic Calorimetry:
BEMC+EEMC+FMS(-1 ≤ ≤ 4)
STAR Decadal Plan 10
Local strong parity violation
• Transitions between domains with different topological charge may induce parity violation in the dense matter– Similar transitions (at much higher energies) might have produced the
matter-antimatter asymmetry in the early universe• Magnetic field in A+A plays a key role: chiral magnetic effect• Crucial to verify if parity violation is the correct explanation
– Beam-energy dependence– Compare collisions of isobaric systems– U+U collisions: collisions with more v2 and less B field than Au+Au
STAR, PRL 103, 251601
STAR Decadal Plan 11
Anti-quark and gluon polarization with 500 GeV p+p
• W measurement will significantly reduce uncertainties on anti-quark polarizations– FGT essential for the forward W’s
• Inclusive jet and di-jet ALL will extend our knowledge of gluon polarization to smaller x
Assumes 600 pb-1 delivered @ P = 50%
STAR Decadal Plan 12
Accessing strange polarization with Λ
• STAR has performed initial Λ DLL measurements at mid-rapidity– Provides access to strange quark polarization– Most interesting with quite high pT Λ (trigger and stat limited)
• Similar measurements at forward rapidity are very promising– Requires the Forward Hadron Calorimeter
STAR Decadal Plan 13
• Does charm flow hydrodynamically?
– Heavy Flavor Tracker: unique access to low-pT fully reconstructed charm
• Are charmed hadrons produced via coalescence?– Heavy Flavor Tracker: unique access to charm baryons
– Would force a significant reinterpretation of non-photonic electron RAA
• Muon Telescope Detector: does J/Ψ flow?
Properties of sQGP: charm
STAR Decadal Plan 14
• Precise measurements with TOF, DAQ upgrade
• Correlated charm in A+A– Decorrelation? Order of
magnitude uncertainty• Address with:
– HFT: D0, displacement– MTD: e-μ correlations
Properties of sQGP: dileptons
STAR Decadal Plan 15
• Muon Telescope Detector: dissociation of Υ, separated by state– At RHIC: small contribution from coalescence, so interpretation clean– No contribution of Bremsstrahlung tails, unlike electron channel
Properties of sQGP: Upsilon
Υ
RHICWhat states of quarkonia is the energy density of matter at RHIC sufficient to dissociate?What is the energy density?
STAR Decadal Plan 16
• Is the mechanism predominantly collisional or radiational?– Detailed, fully kinematically constrained measurements via gamma-
hadron and full jet reconstruction– Pathlength dependence, especially with U+U
• Does the mechanism depend on the parton type?– Gluons: particle identification, especially baryons– Light quarks: gamma-hadron– Heavy quarks: Heavy Flavor Tracker and Muon Telescope Detector
• Does the energy loss depend on the parton energy and/or velocity?– High precision jet measurements up to 50 GeV– Vary velocity by comparing light quarks, charm, and beauty
Mechanism of partonic energy loss
STAR Decadal Plan 17
Jets: proven capabilities in p+pB.I. Abelev et al. (STAR Coll.), Phys.Rev.Lett. 97, 252001, 2006 SPIN-2010: Matt Walker/Tai Sakuma, for the collaboration
• Jets well understood in STAR, experimentally and theoretically
STAR Decadal Plan 18
To date: jets and γ-hadron in A+ATriggered: ~0.3 nb-1 Untriggered: ~0.01 nb-1
• Beginning results from Run 7 indicative, but far from final word
• Huge increase in significance with trigger upgrades+luminosity
• Complementary to LHC– RHIC: quarks; LHC: gluons– Best place to do jets <~ 50 GeV
Phys. Rev. C 82, 034909
STAR Decadal Plan 19
• Sufficient statistical reach out to ~50 GeV for precision measurements– Large unbiased datasets– Trigger upgrades to lessen
bias with walking jet patches
• Smearing of high momentum charged hadrons under control– Corrections: need to calibrate
level of smearing– Hard cutoff in hadrons: small
loss of jets that fragment hard– Dominant uncertainty
fluctuations in the underlying event
Jet capabilities in A+A
STAR Decadal Plan 20
Velocity dependence
• QED: different momenta, different mechanisms• Just beginning the exploration of this space in QCD
“Passage of Particles through Matter”, Particle Data Book
b c light partons
STAR Decadal Plan 21
• What is the velocity dependence of energy loss?– Key tools: heavy quarks with precise kinematic reconstruction– Key technology: Heavy Flavor Tracker and Muon Telescope Detector
Velocity dependence via heavy quarks
STAR Preliminary
STAR Decadal Plan 22
Cold QCD matter
• Hint that RHIC provides unique access to onset of saturation • Compelling and necessary further measurements in future
– Kinematic constraints: large rapidity photons, Drell-Yan in p+A• Same observables very important for our understanding of
transverse spin asymmetries in p+p• Beyond p+p and p+A: the Electron Ion Collider
STAR Decadal Plan 23
Sivers effect sign change
• In SIDIS, knock a colored quark out of a color-neutral nucleon– Quark was bound to the rest of the nucleon before the interaction– Final-state interaction that produces the interference is attractive
• In Drell-Yan, a quark in one hadron annihilates with an anti-quark of the same flavor and opposite color from the other hadron– The rest of the “other hadron” has the same color charge as the
incident quark– Initial-state interaction that produces the interference is repulsive
• Leads to opposite signs for the Sivers effects in the two cases– A key test of the TMD approach
• Similar sign change occurs for direct photon production within the Twist-3 approach
STAR Decadal Plan 24
Other closely related measurements
• AN for W production
– Only measure the electron (or muon)– Can preserve significant sensitivity if measure just above the
Jacobian peak with good pT resolution
• Not clear whether we can achieve sufficient resolution or not
• AN for Z production
– Very easy to interpret– Very small cross section !!!– Not clear if this is practical or not
STAR Decadal Plan 25
MRPC ToF BarrelMRPC ToF Barrel
BBC
FPD
FMS
EMC BarrelEMC End Cap
DAQ1000DAQ1000
COMPLETE
Ongoing R&D
TPC
computing
STAR as of 2014
HFTHFT FGTFGT
MTDMTD
Roman Pots Phase 2
Trigger and DAQ Upgrades
FHC
STAR Decadal Plan 26
STAR forward upgrade
nucleus electron
proton nucleus
To fully investigate the proton spin and cold QCD matter,STAR will move forward
• Positive η: γ and Drell Yan – High precision tracking– e/h and γ/π0 discrimination– Baryon/meson via RICH(?)– Optimized for p+A and p+p– High momentum scale
• Negative η: eRHIC– Optimized for low energy
electrons (1~5 GeV)– Triggering, tracking, ID for
-2.5 <~ η < -1– Can we ID hadrons, too?– R&D necessary for optimal
technology choice
STAR Decadal Plan 27
STAR and eRHIC Phase 1
• Current detector matches quite well to kinematics of eRHIC– Particle ID, sufficent pT resolution, etc. at mid-rapidity
• High Q2 electron scattering• Quark jets from low x events
• A spin example: Explore strange quark polarization at low x– Existing DIS and SIDIS results appear inconsistent
STAR Decadal Plan 28
Energy loss in cold QCD matter
• Complementary probe of mechanism of energy loss• HERMES: mixture of hadronic absorption and partonic loss
– Hadrons can form partially inside the medium • eRHIC: light quarks form far outside medium• Heavy quarks: unexplored to date. Low β: short formation time
Lc up to few 100 fm
RAπ Hermes, Nucl. Phys.B 780, 1 (2007)
STAR Decadal Plan 29
Conclusions
• RHIC and STAR have been extraordinarily successful in their first decade of operations
• The STAR Collaboration has identified compelling physics opportunities for the coming decade
• The STAR Collaboration has identified the detector upgrades required to address these opportunities
• The path forward:– Early in the decade: physics with low mass in the central region– Mid decade: physics of the HFT and MTD– Later in the decade: physics in the forward region
• End of the decade: early phase of eRHIC
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