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POLARISATION@RHIC AND THE “SPIN” STRUCTURE OF THE PROTON
E.C. ASCHENAUER
2E.C. Aschenauer
CONTENT
0 min > 30 min
RHIC Spin group
• changes in the group
• work on polarized pp/ep
Highlights from eRHIC
Summary and Discussion
pC Polarimeters:
• Operation in Run11/12
• Preparation for Run 13+
• Polarisation analysis
• Long term plans
RHIC Spin Program
• What do we know today:
transverse spin phenomena
• Future potentials:
• understand AN
• GPDs at RHIC• Beyond 2015
25 min
RHIC Polarimetry
t
3E.C. Aschenauer
RHIC AND POLARIMETRY
STAR (p)PHENIX (p)
AGS
LINAC BOOSTER
Pol. Proton Source500 mA, 400 ms
Spin RotatorsSolenoid Snake
Siberian Snakes
200 MeV Polarimeter
AGS pC CNI PolarimeterAC Dipole
RHIC pC Polarimeters
Absolute Polarimeter (H jet)
RHIC
Siberian Snakes
Cold Snake
Warm Snake
ANDY (p)
Local Polarimeters STAR and PHENIX
4
RHIC POLARIMETRY
Polarized hydrogen Jet Polarimeter (HJet)Source of absolute polarization (normalization of other polarimeters)Slow (low rates needs looong time to get precise measurements)
Proton-Carbon Polarimeter (pC) @ RHIC and AGS Very fast main polarization monitoring toolMeasures polarization profile (polarization is higher in beam center) and lifetimeNeeds to be normalized to HJet
Local Polarimeters (in PHENIX and STAR experiments)Defines spin direction in experimental areaNeeds to be normalized to HJetAll of these systems are necessary for the
proton beam polarization measurements and monitoring
E.C. Aschenauer
5
RHIC JET RESULTS-RUN12Beam Polarisation at 250 GeV
Analyzing Power24 GeV
Measured beam polarization at injectionRun-11 and Run-12:Run-12 Yellow Beam: 0.63 +- 0.044 have determined AN for pC in one year with one setup
E.C. Aschenauer
Beam Polarisation at 100 GeV
Summary:extremely stable operation through the run
Analysis: A. Dion
6
OPERATION DURING RUN 11 AND 12 Saw significant rate effects during Run 9 250 GeV running
mitigation:o replaced charge sensitive pre-amps by current sensitive ones solved the problem
E.C. Aschenauer
Run 2009
Rate effects: Test pulse applied to all preamps ~500 Hz Monitor pulse rate, amplitude for rate effects:
test pulserate
test pulseamplitude
total pC rate in Si for 72 ch
~ 40% rateloss
amplitudeloss
Run 2011
~ 5% rateloss
NO amplitude
loss
7
RATE CORRECTIONS IN THE AGS CNI POLARIMETER (RUN12)
E.C. Aschenauer
Horizontal Polarization Profile
Polarization in RHIC reference runs
Rate dependence of signal detection efficiency (due to pileup)
(r) = e-kr ≈ 1-krresults in systematic error of polarization measurements
Pmeas. ≈ Ptrue × (1-kr)
In AGS r ≈ 0.1-0.15 (Run12)Naive estimate: k ≈ 0.75
In the 90 degree detectors the rate is strip dependent. It may be employed for experimental determination of the parameter k
45U
90U
90D
45D
Analysis: Andrei Poblaguev
8
OPERATION DURING RUN 11 AND 12
Saw significant rate effects during Run 9 250 GeV running mitigation:
o replaced charge sensitive pre-amps by current sensitive ones
solved the problem
The stable performance of pC allowed to study the non-statistical behaviour of B1/B2 and Y1/Y2 Culprit: the carbon fiber targets
o can move in their holding bracket o fiber can be twistedo measured C kin. energy does not correspond to the one
during scattering Tdet < Tscat assuming wrong AN mitigation: QA stringent control of target width
E.C. Aschenauer
~25nm~7-10mm
changed targetshows clearly normalization per target needed
hard to remove this systematic contribution need different target technology
✔
Analysis: W. Schmidke
9
OPERATION DURING RUN 11 AND 12 Run-12: During 100 GeV running problems with RF induced
noise
mitigation during the run:o Stochastic cooling pickup: terminate one cableo shield pre-amp boxes (Al-wrapping)o install different RF screens in front of SI-detectorso setup test bench using old scattering chambero develop automatic analysis procedure to cut “noisy” channels
mitigation during shutdown:o improve grounding (MUX, terminate unused channels, ….)o redesign pre-amp boxes to shield from RF
Remaining issue:o targets had a incredible death rate (installed twice new full set
during run) o Investigate cause heating through beam full RF simulation of
chambero Possible solutions
different technologies thicker targets possible redesign of target holder
E.C. Aschenauer
good channelbad channel
10
RESULTS FROM OFFLINE ANALYSIS Developed a “offline” online analysis for fast feedback
https://wiki.bnl.gov/rhicspin/Results Determined the pC analyzing power at 24, 100 and 250 GeV
calibration pC to Jet: beam energy independent
E.C. Aschenauer
Beam polarisation decays over the fill polarisation lifetime similar for 100 and 250 GeV basically constant over the years
250GeV
Analysis: Dima Smirnov
11
RHIC PC RESULTS: POLARIZATION PROFILE
H-Jet
p
~1 mm
6-7 mm
pC ColliderExperiments
P1,2(x,y) – polarization profile, I1,2(x,y) – intensity profile, for beam #1 and #2
x=x0
),(),( 01011 yxIyxPP ),(),(),( 2111 yxIyxIyxPP ),(),( 111 yxIyxPP
If polarization changes across the beam, the average polarization seen by Polarimeters and Experiments (in beam
collision) is different
E.C. Aschenauer
12
CORRELATION R-SLOPE AND P-DECAY
E.C. Aschenauer
2009: 100 GeV 2012: 100 GeV2012: 250 GeV
~2-15%/hR=0.07
~4-10%/hR=0.04
~3-5%/hR=0.25
Conclusion:
Polarisation lifetime in a fill is strongly correlated to growth in R
Important to correct for final polarisation numbers for experiments
13
2012 RHIC pC RESULTS: POLARISATION PROFILE
E.C. Aschenauer
Injection
250 GeV
100 GeV
0.25+/-0.011
0.11+/-0.009
0.077+/-0.009 Same pattern in Run-11no difference between x & y profilesee lifetime for R over the fill
Polarisation lifetime has consequences for physics analysis different physics triggers mix over fill see different <P> new information for experiments correct each measurement Pi with Ri
fit P(t)=P0exp(-t/tp) Provide experiments Po(SSA, DSA) and t as well as <P> basically ready for run-9,11 and 12 http://www.phy.bnl.gov/cnipol/fills/
Future Improvements:pJet and pC: move to commercial VME based readout electronics
tested 16ch 250 MHz fADC from Jlab looked perfectpC: main theme for future work improve stability
better targets: movement and thickness stability might be forced to change technology still would like to move to commercial Si detectors better E-resolution, cheaper, off the shelf but saw issues with response from Hamatsu ones
pJet: preventative maintenance main goal improve statistical accuracy of measurement
new Si detectors (500 mm thick) higher t test detectors from Charles University requires also new pre-amp & new ceramics
Longterm: unpolarised jet need to carefully study the trade between statistical accuracy and systematic uncertainties
14
THE RHIC SPIN GROUP
E.C. Aschenauer
15
NEWS FROM THE GROUP Changes in group personnel
Dr. A. Gordon (tenure track) left the group for a job at RENTEC Dec 2012o Dr. Oleg Eyser from UC-Riverside (PHENIX) joined the
group as tenure track in November 2011 Spin PWG convenor at PHENIX
Dr. Alan Dion (H-Jet, STAR) left the group for a permanent position at SBU end of May 2012o currently due to a funding not rehiring
Dr. B. Di Ruzza joined the group as PostDoc to work on the EIC Si-Pixel R&D based on MAPS (funded by an LDRD)
Hire on more postdoc through EIC Detector R&D funds is basically finalized, offer hopefully goes out this weeko dedicated to detector and IR simulations and Detector
R&D (tracking + PID)
Current size of the group:4+1 PostDocs (2 DOE & 1 Director funds & 1 LDRD & 1 EIC Det. R&D)4.5 physicists (3 tenured and 1.5 continuing appointment (0.5 Dr. W. Guryn)2.5 tenure track scientist (0.5 Dr. M. Stratmann)
+ 1 PhD student from China+ 3 undergrads from SBU
E.C. Aschenauer
16
THE RHIC SPIN GROUP
Polarimetry
eRHIC/EIC
PHENIX
STAR
Les BlandAkio OgawaWlodzimierz GurynThomas P Burton Salvatore FazioWilliam B. SchmidkeE.-C. AschenauerDimitri Smirnov
Since 2011E.-C. Aschenauer
Hardware responsibilitiesBBC, FMS-Calib.FGTRoman Pots of pp2pp
Forward Upgrade
Physics goals: Forward Physics in dAu gluon saturation CGC
Single Spin AsymmetriesAN Jet, W, Di-jetGPDspp2pp: diffractive physics & glueball searches
Alexander BazilevskyOleg Eyser
Hardware responsibilitiesA. Bazilevsky:Trigger coordinator Run11&12
ePHENIXsPHENIX forward upgrade
Physics goals:DG & cross section via p0, AL W-physicsDrell-Yan in pptransverse physics observables
O. EyserSpin PWG convener
Elke-C. AschenauerAlan Dion < May 2012Oleg Eyser > nowWilliam B. SchmidkeDimitri Smirnov A. Kirleis (undergrad)
Hardware responsibilities: pC polarimeters, H-Jet detectorsImprovements of the PolarimetersDAQ Physics goals:Offline analysis of polarimeter data final polarization for experiments
Fast feedback to CAD to improve polarization in RHIC
Elke-C. AschenauerThomas P Burton Salvatore FazioBenedetto di Ruzzo+ ! postdocLiang Zheng (PhD)+ 2 undergrads
Responsibilities: Detector Design & IR integrationhadron polarimetry“Roman Pots”Software toolsEIC-White-Paper Physics goals:ep: Spin, TMDs, GPDseA: determine initial and final state effects/conditions
ECA Co-convener of the BNL EIC-TF
Les BlandAkio Ogawa
Remaining Physicsgoals:analyze data from run-11
ANDY
• Postdocs: funded by LDRDs and Director’s Funds• Postdocs: funded by DOE ME
E.C. Aschenauer
17
GROUP ACHIEVEMENTS
Papers: STAR:
o 1 paper published + 3 submitted o 2 with contributions from the RHIC spin group
PheniX:o 1 published + 1 submitted o 1 with contributions from the RHIC Spin Group
several Papers not on RHIC from earlier involvementso HERMES, Zeus, D0, CDF, ….
~40 Seminars and Presentations on Conferences and Workshops
E.C. Aschenauer
18
THE RHIC SPIN PROGRAM
E.C. Aschenauer
19
COLLECTED LUMINOSITY WITH LONGITUDINAL POLARIZATION
Year Ös [GeV]Recorded PHENIX
RecordedSTAR Pol [%]
2002 (Run 2) 200 / 0.3 pb-1 15
2003 (Run 3) 200 0.35 pb-1 0.3 pb-1 27
2004 (Run 4) 200 0.12 pb-1 0.4 pb-1 40
2005 (Run 5) 200 3.4 pb-1 3.1 pb-1 49
2006 (Run 6) 200 7.5 pb-1 6.8 pb-1 57
2006 (Run 6) 62.4 0.08 pb-1 48
2009 (Run9) 500 10 pb-1 10 pb-1 39
2009 (Run9) 200 14 pb-1 25 pb-1 55
2011 (Run11) 500 27.5 / 9.5pb-1 12 pb-1 48
2012 (Run12) 500 30 / 15 pb-1 82 pb-1 50/54
E.C. Aschenauer
20
DQ: W PRODUCTION BASICS
u
d
Since W is maximally parity violating W’s couple only to one parton helicitylarge Δu and Δd result in large asymmetries.
No Fragmentation !high Q2
Similar expression for W- to get Δ and Δd…
E.C. Aschenauer
21
THE POLARISATION OF THE SEA QUARKS
E.C. Aschenauer
Current Results:
22
WHAT CAN BE EXPECTED
E.C. Aschenauer
allows for flavor separation for 0.07 < x < 0.04
Δχ2 = 2% uncertainty bands of DSSV analysis
Δχ2 = 2% uncertainty bands with RHIC data
All W-related upgradeswill be or have been already installed for Run 13.PHENIX: RPC and m-Triggerhave been completed before RUN 12STAR: FGT will be fully installed
With a 15 week run in 2013 equally fantastic as the
one in 2012, we can come close to
the required ∫ luminosity
23
DG: WHAT DO WE KNOW
E.C. Aschenauer
World DIS Data & RHIC till 2006
RHICDIS
terra incognita
consistent with
p0 data
First time significant non zero Dg(x) 0.01<x<0.2What now: try to go to terra incognita
lower x the ultimate answer only from eRHIC
24
DG WHAT WILL COME
E.C. Aschenauer
uncertainties decrease by ~20% if Run 12+13
are combined
uncertainties decrease by ~1.4 if Run 12+13 are combined
of course many other channels both from PHENIX and STARbut with less statistical power
x>0.001
After run-14 we will have a nice set of high
statistics data to determine Dg(x) for x > 0.01
and started measurements to explore lower x
25
COLLECTED LUMINOSITY WITH TRANSVERSE POLARIZATION
Year Ös [GeV]Recorded
PHENIXRecorded
STAR Pol [%]
2001 (Run 2) 200 0.15 pb-1 0.15 pb-1 15
2003 (Run 3) 200 / 0.25 pb-1 30
2005 (Run 5) 200 0.16 pb-1 0.1 pb-1 47
2006 (Run 6) 200 2.7 pb-1 8.5 pb-1 57
2006 (Run 6) 62.4 0.02 pb-1 53
2008 (Run8) 200 5.2 pb-1 7.8 pb-1 45
2011 (Run11) 500 / 25 pb-1 48
2012 (Run12) 200 9.2/4.3 pb-1 22 pb-1 61/58
E.C. Aschenauer
26
TRANSVERSE POLARIZATION EFFECTS @ RHIC
Left
Right
midrapidity: maybe gluon Sivers????
Big single spin asymmetries in pp !!
Naive pQCD (in a collinear picture) predicts AN ~ asmq/sqrt(s) ~ 0
What is the underlying process?Sivers / Twist-3 or Collins or ..
no answer yet
Do they survive at high √s ? ✔Is pt dependence as expected from p-QCD? NO
E.C. Aschenauer
27
TRANSVERSELY POLARIZED PROTON MC
Collins with positivity bounds as input
Fast smearing generator tool to smear generator particle responses in p and energy and to include PID responses, “detectors” can be flexible defined in the acceptance
Developed by Tom Burton also for eRHIC
Sivers and Collins asymmetries included
IFF and DY/ W AN need to be still included
Details: http://drupal.star.bnl.gov/STAR/system/files/burtonAnalysisMeeting20110418.pdf Sivers Mechanism
E.C. Aschenauer
28
WHAT ELSE DO WE KNOW
Collins / Transversity: conserve universality in hadron hadron interactions FFunf = - FFfav and du ~ -2dd evolve ala DGLAB, but soft because no gluon
contribution (i.e. non-singlet) Sivers, Boer Mulders, ….
do not conserve universality in hadron hadron interactions
kt evolution can be strongo till now predictions did not account for evolution
FF should behave as DSS, but with kt dependence unknown till today
u and d Sivers fct. opposite sign d >~ u Sivers and twist-3 are correlated
o global fits find sign mismatch, possible explanations, like node in kt or x don’t work
E.C. Aschenauer
29
AN: HOW TO GET TO UNDERLYING PHYSICS
SIVERS Transversity x Collins
AN for jets in mid to forward rapidity AN for direct photons in mid to forward rapidity
AN for heavy flavour gluon
p+/-p0 azimuthal distribution in jets mid to forward rapidity Interference fragmentation function mid to forward rapidity
AN for p0 and h in FMS with increased pt coverage
STAR: Combine 2011 transverse 500 GeV dataand 2012 transverse 200 GeV data
Powerful dataset to attack AN mysteryand it will help us to optimize forward upgrades
planned by PHENIX and STAR
E.C. Aschenauer
30
STAR: MID-RAPIDITY SURPRISE
E.C. Aschenauer
Exploratory Analysis from 200 GeV Transverse Running in 2006 show first clear signal of transversity in pp collisions at RHIC!
IFF Asymmetry
Collins
IFF
31
THE FAMOUS SIGN CHANGE OF THE SIVERS FCT.
E.C. Aschenauer
QLQCD QT/PT <<<<QT/PT
Collinear/twist-3
Q,QT>>LQCD
pT~Q
Transversemomentumdependent
Q>>QT>=LQCD
Q>>pT
Intermediate QT
Q>>QT/pT>>LQCD
Sivers fct.Efremov, Teryaev;
Qiu, Sterman
DIS: attractiveFSI
Drell-Yan: repulsiveISI
QCD:
SiversDIS = - SiversDY / SiversW
critical test for our understanding of TMD’s and TMD factorization
Electrons and positrons from hard QCD processes are uncorrelated Opening angles are comparable to Drell Yan: detector
acceptance Lepton energies of
Drell Yan decays are large
Energy cut removes QCD background at small minv
Large masses in QCDbackground favor mid-rapidity
Energy asymmetry hasnot been instrumented yet
BACKGROUND REJECTION
32E.C. Aschenauer
Study: O. Eyser
• Parametrized fast MC for detectorsmearing
• Drell Yan signal– 3 – 10 GeV/c2
• Energy cut– E1,2 > 2 GeV
• Forward rapidities – Effectively no
background left– Statistically limited
– Drell Yanfor minv < 3 GeV/c2 not physical (PYTHIA settings)
DRELL-YAN AT FORWARD RAPIDITIES
33E.C. Aschenauer
34
THE POLARIZED DY/W AN CHALLENGE Caveat: kt evolution of TMDs
First results from evolution workshop at Jlabhttp://www.jlab.org/conferences/qcd2012/program.html
Need to see how things develop
!
If this strong evolution effect is
really true ?
E.C. Aschenauer
HP-13: Test unique QCD predictions for relations between single-transverse spin phenomena in p-p scattering and those observed in deep-inelastic lepton scattering.
Can we do it ? Yes we can !Many accessible observables An
jet, Ang with very clear predictions
based on SIDIS measurements
AN(DY/W): Sign change and evolution are strong prediction of “TMD-formalism” need to measure to see predictions are true
35
THE RHIC SPIN Program > 2015
going forward map out transverse spin effects
potential to get the first glimpse of GPD E for gluons low-x gluons
E.C. Aschenauer
36
FROM PP TO gP/A
Get quasi-real photon from one proton Ensure dominance of g from one identified proton by selecting very small t1, while t2 of “typical hadronic size” small t1 large impact parameter b (UPC) Final state lepton pair timelike compton scattering timelike Compton scattering: detailed access to GPDs including Eq;g if have transv. target pol. Challenging to suppress all backgrounds
Final state lepton pair not from g* but from J/ψ Done already in AuAu Estimates for J/ψ (hep-ph/0310223)
transverse target spin asymmetry calculable with GPDs
information on helicity-flip distribution E for gluons golden measurement for eRHIC
Gain in statistics doing polarized p↑A
Z2
A2
E.C. Aschenauer
37
FORWARD PROTON TAGGING AT STAR/RHIC
• Roman Pot detectors to measure forward scattered protons in diffractive processes
• Staged implementation to cover wide kinematic coverage Phase I (Installed): for low-t coverage
Phase II (planned) : for higher-t coverage
8(12) Roman Pots at ±15 and ±17m
2π coverage in φ will be limited due to
machine constraint (incoming beam) No special b* running needed any more 250 GeV to 100 GeV scale t-range by 0.16
at 15-17mat 55-58m
E.C. Aschenauer
J.H. LeeStudy: JH Lee & W. Guryn
38
STAR FORWARD INSTRUMENTATION POSSIBILITIES
E.C. Aschenauer
FMS
~ 6 GEM disksTracking: 2.5 < η < 4
Threshold Cerenkovp+/- ID
Preshower1/2” Pb radiatorShower “max”
proton nucleus > 2016
HCal
SPACAL
39
THE sPHENIX FORWARD UPGRADE
E.C. Aschenauer
40
WHAT pHE3 CAN TEACH US Polarized He-3 is an effective neutron target d-
quark target Polarized protons are an effective u-quark target
Therefore combining pp and pHe3 data will allow a full quark flavor separation u, d, ubar, dbar
Two physics trusts for a polarized pHe3 program: Measuring the sea quark helicity distributions through W-production
Access to Ddbar Caveat maximum beam energy for He-3: 166 GeV
Need increased luminosity to compensate for lower W-cross section
Measuring single spin asymmetries AN for pion production and Drell-Yan expectations for AN (pions)
similar effect for π± (π0 unchanged)3He: helpful input for
understanding
of transverse spin phenomena
Critical to tag spectator protons from 3He with roman potsE.C. Aschenauer
41
SPECTATOR PROTON FROM 3HE WITH THE CURRENT RHIC OPTICS
The same RP configuration with the current RHIC optics (at z ~ 15m between DX-D0) Acceptance ~ 98%
Accepted in RPPassed DX aperturegenerated
Momentum smearing mainly due to Fermi motion + Lorentz boost Angle <~3mrad (>99.9%)
An
gle
[ra
d]
E.C. Aschenauer
Study: JH Lee
42
THE HIGHLIGHTS FROM eRHIC
E.C. Aschenauer
43
THE PATH TO IMAGING QUARKS AND GLUONS
How are GPDs characterized?
unpolarized polarizedconserve nucleon helicity
flip nucleon helicitynot accessible in DIS
DVCS
quantum numbers of final state select different GPD
pseudo-scaler mesons vector mesons
PDFs do not resolve transverse momenta or positions in the nucleon fast moving nucleon turns into a `pizza’ but transverse size remains about 1 fm
compelling questions
how are quarks and gluons spatially distributed
how do they move in the transverse plane
do they orbit and do we have access to spin-orbit correlations
transverse
plane
DVCS: Golden channel theoretically clean wide range of observables (s, AUT, ALU, AUL, AC) to disentangle different GPDs
DVCS AT eRHIC
44
e’(Q2)
e gL*
x+ξ x-ξ
H, H, E, E (x,ξ,t)~~
g
p p’t
D. Mueller, K. KumerickiS. Fazio, M. Diehl and ECA
E.C. Aschenauer
DVCS data at end of HERA
needs100 fb-1
needs10 fb-1
+ Roman Pots
small t
large t
45
WHAT WILL WE LEARN ABOUT 2D+1 STRUCTURE OF THE PROTON
GPD H and E as function of t, x and Q2GPD H and E 1d+1
GPD H and E 2d structure for quarks
Plots from D. Mueller
A global fit over all mock data was done, based on the GPDs-based model:
[K. Kumerički, D Müller, K. Passek-Kumerički 2007]
Known values q(x), g(x) are assumed for Hq, Hg (at =0, t=0 forward limits Eq, Eg are unknown)
Excellent reconstruction of Hsea, Hsea and good reconstruction of Hg (from dσ/dt)
E.C. Aschenauer
shift due to GPD E
46E.C. Aschenauer
IMPACT OF EIC DATA ON HELICITY PDFs DIS scaling violations mainly
determine Δg at small x SIDIS data provide detailed flavor
separation of quark sea can be pushed to x=10-4 with 20 x
250 GeV data
Study: M. Stratmann, R. Sassot, ECA
47
DIS scaling violations mainly determine Δg at small x ( SIDIS scaling violations add to this)
in addition, SIDIS data provide detailed flavor separation of quark sea
IMPACT OF EIC DATA ON HELICITY PDFs
• includes only “stage-1 data” [even then Q2
min can be 2-3 GeV2]
• can be pushed to x=10-4 with 20 x 250 GeV data [still one can play with Q2
min ]
• uncertainties determined with both Lagrange mult. & Hessian
“issues”:
• (SI)DIS @ EIC limited by systematic uncertainties need to control rel. lumi, polarimetry, detector performance, … very well
• QED radiative corrections need to “unfold” true x,Q2
well known problem (HERA) BNL-LDRD project to sharpen tools
E.C. Aschenauer
48
• combined correlated uncertainties for ΔΣ and Δg
• can expect approx. 5-10% uncertainties on ΔΣ and Δg
but need to control systematics
current data
w/ EIC data
• similar improvement for 0.0001-1 moments needs 20 x 250 GeV data
• results obtained with two Lagrange multipliers
Hessian method consistent
PROGRESS TOWARDS SPIN SUM RULE
E.C. Aschenauer
“Helicity sum rule”
totalquark spin
angular momentum
gluonspin
✔
✔access through
Twist-3 GPDsmore theoretical
work needed
“X. Ji sum rule”
difficult,but should be
possible in GPD models
✔
49
SUMMARY
E.C. Aschenauer
SqDq
DG
Lg
SqLq
dq1Tf
SqDq
DG
Lg
SqLq dq1Tf
HP-122013
HP-82013
HP-132015
RHIC spin active program with many new developmentsin theory and experiments!On track to achieve milestones
Where do we stand to unravel the internal structure of protons
50
BACKUP
RHIC-AGS User Meeting 2012
51
THE eA PHYSICS PROGRAM
E.C. Aschenauer
The Initial Conditions
time
CGCJIMWLK/BK Hydro (EoS)
Hard Processes
(pQCD)
FF/coal.Hadron
Transport IOur understanding of some fundamental
properties of the Glasma, sQGP and Hadron Gas depend strongly on our
knowledge of the initial state!
3 conundrums of the initial state:1. What is the spatial transverse distributions
of nucleons and gluons?2. How much does the spatial distribution fluctuate? Lumpiness, hot-spots etc.3. How saturated is the initial state of the nucleus?
RHIC-AGS User Meeting 2012
52
IS THE sQGP A PERFECT FLUID?
E.C. Aschenauer
IP-GLASMA
KLN-CGC
GlauberWood-Saxon
AdS/CFT predicts for a perfect fluid:η/s = 1/(4π) ~ 0.08
Schenke, Tribedy, Venugopalan arXiv:1202.6646
Different initial states =different fluctuation scales
RHIC-AGS User Meeting 2012
53
h-h FORWARD CORRELATION IN p(d)A AT RHIC
Small-x evolution ↔ multiple emissions Multiple emissions → broadening Back-to-back jets (here leading hadrons) may get
broadening in pT with a spread of the order of QS
Ap p
large-x1 (q dominated)
low-x2 (g dominated)
side-view beam-view
π
Low gluon density (pp):pQCD predicts 2→2 process ⇒ back-to-back di-jet
High gluon density (pA):2 → many process⇒ expect broadening of away-side
First prediction by: C. Marquet (’07)Latest review: Stasto, Xiao, Yuan arXiv:1109.1817 (Sep. ’11)
E.C. Aschenauer
RHIC-AGS User Meeting 2012
54
FORWARD CORRELATIONS IN dA AT RHIC
Away side parton randomized by strong color field
+offset
Kang, Vitev, Xing arXiv:1112.6021v1
Albacete, Marquet
1 question, 2 answers
How saturated is the initial state?
Initial state saturation model
“Non-initial state” shadowing model
+offset
B. Xiao et al. 2012
E.C. Aschenauer
RHIC-AGS User Meeting 2012
55
eRHIC: REACHING THE SATURATION REGION
HERA (ep):Despite high energy range: F2, Gp(x, Q2) outside the saturation regime Need also Q2 lever arm! Only way in ep is to increase √s Would require an ep collider at √s ~ 1-2 TeV
Different approach (eA):
L ~ (2mN x)-1 > 2 RA ~ A1/3
Probe interacts
coherently with all nucleons
E.C. Aschenauer
Gold: A=197, x 197 times smaller!
RHIC-AGS User Meeting 2012
56
DIHADRON CORRELATIONS IN eA AT EIC
EIC:
Extract the spatial multi-gluon correlations and study their non-linear evolution
o essential for understanding the transition from a deconfined into a confined state.
Advantage over p(d)A:
eA experimentally much cleaner
o no “spectator” background to subtract
o Access to the exact kinematics of the DIS process (x, Q2)
Either jets or use leading hadrons from jets (dihadrons)
Perfect saturation signature:
E.C. Aschenauer
RHIC-AGS User Meeting 2012
57
EIC: eA DIHADRON CORRELATIONS STUDIES
Dominguez, Xiao, Yuan, Lee, Zheng ‘11/12
Theory: SaturationExp: Saturation versus“conventional” scenario
eA-MC: Pythia6.4 + nPDF (EPS09) + nuclear geometry from DPMJetIII without PS
Here for 10 fb-1/A (~ 20 weeks), std. experimental cuts Clear signal, pronounced differences between sat and no-sat
E.C. Aschenauer
RHIC-AGS User Meeting 2012
58
HARD DIFFRACTION IN DIS AT SMALL X
• Diffraction in e+p:‣ coherent ⇔ p intact‣ incoherent ⇔ breakup
of p‣ HERA: 15% of all events
are hard diffractive
• t = (p-p’)2
• β is the momentum fraction of the struck parton w.r.t. the Pomeron
• xIP = x/β: momentum fraction of the exchanged object (Pomeron) w.r.t. the hadron
• Diffraction in e+A:‣ coherent diffraction (nuclei intact)‣ breakup into nucleons (nucleons
intact)‣ incoherent diffraction‣ Predictions: σdiff/σtot in e+A ~25-40%
e+p
E.C. Aschenauer
RHIC-AGS User Meeting 2012
59
WHY IS DIFFRACTION SO IMPORTANT
Sensitive to spatial gluon distribution
Hot topic: Lumpiness? Just Wood-Saxon+nucleon g(b)
Incoherent case: measure fluctuations/lumpiness in gA(b)
Sensitive to gluon momentum distributions s ~ g(x,Q2)2
E.C. Aschenauer
RHIC-AGS User Meeting 2012
60
EXCLUSIVE VECTOR MESON PRODUCTION
Golden channel: e + A → e’ + A’ + VM‣ Only channel where t can be
derived from VM and e’‣ Detecting neutron emission from
nuclear breakup allows to separate coherent from incoherent
Dipole Cross-Section:
J/ψϕ
E.C. Aschenauer
RHIC-AGS User Meeting 2012
61
DIFFRACTION SENSITIVE TO SATURATION
Simple but effective
Measurement: σDiff(eA)/σDiff(ep)/A4/3
as fct. of Q2
Coherent events only scale with A4/3 for large Q2
Sartre event generator based on dipole modelo describes HERA
data nosat: dipole cross-
section linearized Clear difference in
model prediction between sat and nosat
sat
sat
nosat
nosat
J/ψ
φ
E.C. Aschenauer
RHIC-AGS User Meeting 2012
62
eRHIC: INCLUSIVE DIFFRACTION
E.C. Aschenauer
Can constrain models a lot with a few months of running!
Already in Stage 1!
63
de Florian, Vogelsang
EXPECTATIONS FOR ALE IN PP COLLISIONS
t large u large
strong sensitivity to
t large u large
limited sensitivity toE.C. Aschenauer
64
• latest twist: “sign mismatch”
1st kT moment of Sivers fct and twist-3 analogue related at operator level
Kang, Qiu, Vogelsang, Yuan
Boer, Mulders, Pijlman;Ji, Qiu,, Vogelsang, Yuan
both sides have been extracted from data
find: similar magnitude ✓but wrong sign ✖
inconsistency in formalism?
possible resolutions: (1) data constrain Sivers fct only at low kT; function has a node
(2) analysis of Tq,F neglects possible final-state contributions to AN
phenomenological studies with more flexible Sivers fct. under wayKang, Prokudin
need data for AN which are insensitive to fragmentation: photons, jets, DY
• on the bright side: recent progress on evolution for Sivers fctKang, Xiao, Yuan
crucial for consistent phenomenology – properly related experiments at different scales
FROM SIGN CHANGES TO SIGN MISMATCHES
E.C. Aschenauer
65
LAST BUT NOT LEAST: RHIC POLARIMETRY
After problems with the CAMAC modules in the tunnelY2U and B2D electronics moved also back to the counting house (mid Feb.)
RHIC pC Setup Run-11
E.C. Aschenauer
66
MUCH MORE DATA ON TAPE AND TO COME
Phys. Rev. D 79, 012003 : √s = 62.4 GeV
Direct photon
η ALL : Phys. Rev. D 83, 032001
Increased √s allows to go to lower x Different final states select between gg and qg scattering sign of Dg Future measurements will include di-hadron at forward rapidity constrain x and to go to lower x
2-2.5 GeV/c4-5 GeV/c9-12 GeV/c
2-2.5 GeV/c4-5 GeV/c9-12 GeV/c
E.C. Aschenauer
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