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

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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