Jet Production from p + p at STAR

James L. DrachenbergFor the STAR Collaboration

October 1, 2013

OUTLINE Introduction Event Selection Analysis Description Systematic Uncertainties Preliminary Results ConclusionsTransverse Single-spin Asymmetries fromp + p jet + X and p + p jet + +Xat s = 500 GeV at RHIC

STAR

----- Meeting Notes (9/26/13 09:50) -----STAR in titleearly-on mention first-time results0

Contributions to Proton Spin Structure

Consider proton moving rightq(x)g(x)Proton spin Spin sum rule:Polarized DIS: ~ 0.3coming into focus:h1(x)Proton spin Transversity data over limited kinematic range: xBj 0.31Transverse-spin Jet Asymmetries - Drachenbergpoorly constrained

arXiv:nucl-ex/1304.0079 1By now, were all quite familiar with this picture of the proton and the famous sum-rule with contributions from Dsigma, DG, and parton orbital angular momentum. While we know Dsigma quite well from polarized DIS, were only recently beginning to probe DG while orbital angular momentum is still quite unconstrained. Additionally, while we have data on quark transversity, it is only over a limited range of Bjorken-x. So, we are still quite interested in ways we can probe these two pieces of proton spin structure.--*orbital* angular momentumpossibly quicker here2Transverse-spin Jet Asymmetries - DrachenbergSeparate Sivers and Collins:Go beyond inclusive production - e.g. Jets, correlations, direct photonsSivers ~ sin(S)Collins ~ sin(S-h)Sangle between spin and event planehangle of hadron around jet axisSensitivity to Orbital Motion and Transversity?SP (p kT,parton) 0Sq (p kT,) 0Sivers mechanism: asymmetry in the forward jet or productionSPkT,partonppCollins mechanism: asymmetry in the forward jet fragmentationSPppSqkT,Sensitive to proton spin parton transverse motion correlations (needs Lz)Sensitive to transversity (h1) Kinematic Variablesz = p / pjetjT (kT, ) = pT relative to jet axis2As weve heard, there are a couple of possible ways one might access information on orbital angular momentum and transversity. First, consider the Sivers effect. Here, the transverse polarization of the proton is correlated with the internal transverse momentum of the parton, resulting in an azimuthal asymmetry in the jet production. Some models suggest this effect might be sensitive to parton orbital motion. On the other hand, the Collins effect suggests that inside the transversely polarized proton resides a transversely polarized quark. The polarization of this quark is transferred through the hard-scattering where it undergoes a fragmentation where the polarization of the quark is correlated with the transverse momentum of the fragmenting pion, say. Now, for this effect to be nonzero, requires nonzero transversity. Thus, it is possible that these two effects may yield information on these somewhat unconstrained aspects of proton spin structure. Now, for the inclusive hadron asymmetries weve seen, it is possible that both of these effects are at play, manifesting as an azimuthal asymmetry in the hadron production.

To isolate each contribution, one needs to go beyond, say, inclusive pions, to measurements of, e.g. jets, di-hadron correlations, or direct photon, which is insensitive to fragmenation. So, for jet measurments, the Sivers effect manifests as an azimuthal asymmetry in the jet production, itself. On the other hand, the Collins effect manifests itself not as an asymmetry in the jet production, but rather in the azimuthal distribution of hadrons within the jet.----- Meeting Notes (9/26/13 11:10) -----clarify what I mean by what BELLE measuredTransverse Jet Asymmetries3Transverse-spin Jet Asymmetries - DrachenberghpbeampbeamSpPJETjTSF. Yuan, PRL 100, 032003 (2008)DAlesio et al., PRD 83, 034021 (2011)Transverse Momentum Dependent (TMD) ApproachAsymmetry moments sensitive to various contributions(analogous moments sensitive to gluon scattering)

AUT Transverse single-spin asymmetry (also written AN)

Transversity Boer-Mulders FFPretzelocity Boer-Mulders FFSivers Boer-Mulders Collins3[Elke]

very nice slide, just a cosmetic suggestion, in the nice table maybe use colors to correlated the symbols to the english names.

[Anselm]

all the moments might just confuse (e.g. pretzelosity)

----- Meeting Notes (9/26/13 11:10) -----not too much time

Transversity Boer-Mulders FFPretzelocity Boer-Mulders FFSivers Boer-Mulders CollinsTransverse Jet Asymmetries4Transverse-spin Jet Asymmetries - DrachenberghpbeampbeamSpPJETjTSF. Yuan, PRL 100, 032003 (2008)DAlesio et al., PRD 83, 034021 (2011)Transverse Momentum Dependent (TMD) ApproachAsymmetry moments sensitive to various contributions(analogous moments sensitive to gluon scattering)

AUT Transverse single-spin asymmetry (also written AN)4[Elke]

very nice slide, just a cosmetic suggestion, in the nice table maybe use colors to correlated the symbols to the english names.

[Anselm]

all the moments might just confuse (e.g. pretzelosity)

----- Meeting Notes (9/26/13 11:10) -----not too much time

Phys. Rev. D 86 32006 (2012)STAR Transverse Jet Asymmetries at Central Pseudorapidity5Transverse-spin Jet Asymmetries - DrachenbergSTAR measured transverse single-spin asymmetries for inclusive jet production at central pseudorapidity and s = 200 GeV (2006)

: consistent with zero

: hints of non-zeroasymmetry with charge-sign dependence

Similarly, di-jet and 0 AN at central psuedorapidityand 200 GeV consistent with zeroPRL 99, 142003, PRL. 95, 202001, arXiv:hep-ex/1108.0911

R. Fersch, DNP2011

Collins Asymmetry A 2 vs. jTCollins Asymmetry A 2 vs. z0.2 0.4 0.6 0.8z-0.10.12 10-1 1 10jT (GeV)5Now, STAR has recently published measurements of jet A_N, now isolating the contribution of the Sivers mechanism. Here you see, A_N as a function of jet p_T for several bins of pseudorapidity from data taken in Run-6 at 200 GeV. And you can see that to the current precision these asymmetries are consistent with zero. Here you see some model estimates from DAlesio and Co. of the maximal Sivers asymmetry, and it appears these jet measurements fall well below these limits. Additionally, if one considers the various projections from SIDIS in this model, the asymmetries appear to be below the projection for the gluon Sivers contribution. Similarly, measurements of the asymmetry from di-jets also are consistent with zero, below what one might expect from SIDIS. Recent datasets from Run-12 should provide much higher statistics for these measurements at 200 GeV.

STAR Transverse Jet Asymmetries at Central Pseudorapidity6Transverse-spin Jet Asymmetries - Drachenberg2012 STAR data provide opportunity for higher precision and greatly reduced systematic uncertainties at s = 200 GeV2011 STAR data provide opportunity for first measurements of central pseudorapidity inclusive jet asymmetries at s = 500 GeV Increased sensitivity to gluonic subprocesses

pT [GeV/c]

Aschenauer, JLab UGM 2013

R. Fersch, DNP20116Also, STAR has reported measurements for the Collins asymmetry for charged pions within jets, and here, it appears one may be seeing hints of a signal. This, perhaps, indicates one may be able to constrain transversity in jet measurements at RHIC at these higher reaches of x. Now, in these data from Run-6, our uncertainties are still quite large, however, again, Run-12 provides an opportunity to reduce both the statistical and systematic uncertainties from these Run-6 measurements.

----- Meeting Notes (9/26/13 11:10) -----Clarify lower left-hand plot?

Moments of Jet Asymmetries at 500 GeV7Transverse-spin Jet Asymmetries - DrachenbergVarious contributions to polarized jet+ cross section (TMD approach)

Phys. Rev. D 83, 034021 (2011)7

Phys. Rev. D 83, 034021 (2011)Moments of Jet Asymmetries at 500 GeV8Transverse-spin Jet Asymmetries - DrachenbergNegligible under maximized scenario!Various contributions to polarized jet+ cross section (TMD approach)8

Phys. Rev. D 83, 034021 (2011)Moments of Jet Asymmetries at 500 GeV9Transverse-spin Jet Asymmetries - DrachenbergPossible non-zero contributions, expected to be quite smalle.g. Phys. Rev. Lett. 95, 202001 (2005);Phys. Rev. Lett 99, 142003 (2007);Phys. Rev. D 86, 032006 (2012);arXiv:hep-ex/1108.0911

projections for s = 500 GeVDAlesio et al.Various contributions to polarized jet+ cross section (TMD approach)9Moments of Jet Asymmetries at 500 GeV10Transverse-spin Jet Asymmetries - DrachenbergCollins-like asymmetry:Sensitive to linearly polarized gluonsCompletely unconstrained!

Phys. Rev. D 83, 034021 (2011)

Maximized contributionfor s = 500 GeVDAlesio et al.Various contributions to polarized jet+ cross section (TMD approach)

Gluon helicity density matrixOff-diagonal terms related to linear polarization in (xy) plane at angle to x-axisPhys Rev. D 73, 014020 (2006)10

Solenoidal Tracker at RHIC11Transverse-spin Jet Asymmetries - DrachenbergJet reconstruction utilizesTPC + Barrel + Endcap EMCMinbias Trigger: coincidence invertex position detector (VPD)Pb+plastic scintillator with PMT readout570 cm from interaction point4.24 < || < 5.1,

J. Zhou, M.S. Thesis

11Now, at STAR we have active groups measuring both inclusive hadron asymmetries, as well as jets and di-hadrons. Here, you see the familiar diagram of the STAR detector. We utilize our Endcap Electromagnetic Calorimeter as well as our Forward Meson Spectrometer and Forward Pion Detector which is off the edge of the slide for measuring inclusive pions and etas which have been of interest to model predictions based on, e.g., twist-3 pQCD as well as these transverse-momentum-dependent models like Sivers and Collins. Also, at STAR we use our large-acceptance TPC and Barrel Electromagnetic Calorimeter to do full jet reconstruction and di-hadron asymmetries, e.g., to isolate the effects of transversity.

----- Meeting Notes (9/26/13 11:10) -----point to pictureJet Reconstruction in STAR12Transverse-spin Jet Asymmetries - DrachenbergAnti-kT algorithmJHEP 0804, 063 (2008)

Radius parameter R = 0.6Use PYTHIA + GEANT to quantify detector response

STAR Di-jet event at detector-level

e-e+DetectorGEANTPYTHIA

Data jets MC jetsParticleParton Kinematic Variablesz momentum / jet momentumjT pT relative to jet axis12[Anselm]

go slowly, this is pretty much star lingo I think,

2011 STAR Event Selection13Transverse-spin Jet Asymmetries - DrachenbergCenter of mass energy, s = 500 GeVTotal integrated luminosity of 25 pb-1 for all transverse runsPolarization for present analysis: 543%Good event vertex with |zvertex| < 30 cmJet Reconstruction:Nhits, track > 12Track association with event vertexMinimum track pT > 0.2 GeV/cMinimum tower energy > 0.2 GeVJet requirements:No charged particles with pT > 30 GeV/cTotal charged-particle pT > 0.5Neutral-energy fraction < 0.98|jet| < 1.0 (and within detector acceptance of BEMC+TPC)6 < pT,jet < 55 GeV/cPion Requirements:Restriction on dE/dx: -1 < n() < 2.5 (contamination < 3%)(jet-ch)2 + (jet-ch)2 > (0.1)2Nhits, dE/dx > 513----- Meeting Notes (9/26/13 11:10) -----don't rush, but hit only bullet pointsmention combining track hits+calorimeter depositsStudies with Embedded Monte Carlo14Transverse-spin Jet Asymmetries - DrachenbergSystematic shifts in reconstructed kinematic variables and azimuthal resolutions evaluated by comparing to Monte Carlo embedded in real zero-bias datasimulate effects of real, out-of-time pile-up

Detector-level jets matched both toparton and particle jets with matched event vertexKinematic shifts evaluated at particle levelCorresponding parton-jet pT ~0.6-1.4 GeV/c lower

jet pTtrack ztrack jT14

Sources of Systematic Uncertainty15Transverse-spin Jet Asymmetries - Drachenberg

Pion contamination < 3%Dominant systematic uncertainty fromreconstructed jets unassociated with parton jets Take difference between measured AUT and AUT assuming dilution

Further systematic uncertainties:Resolution of relevant azimuthal angles corrected as dilution to measured asymmetryleak-through of other moments of AUTPion contamination from K/p and e (< 3%)Polarization uncertainty (correlated vertical scale uncertainty, (P)/P = 5.6%)Angular resolution corrected as dilution15----- Meeting Notes (9/26/13 11:10) -----more time explaining dilutionexplain pion cuts?Asymmetry Measurements16Transverse-spin Jet Asymmetries - Drachenberg

For uniform acceptance:

and yields are functions of integrated over

half of detector16Now, as we mentioned, for jet and di-hadron measurements it is possible to decouple the Collins and Sivers mechanisms. Say we have a polarized beam headed into the board with polarization in the y-direction, with x in this direction. We can divide the detector space into upper and lower halves, for instance. The production yields in each half are functions of two angles: phi_S, the azimuthal angle between the polarization and the jet (or di-hadron) axis, and phi_h which is is the azimuthal angle of the pion around the jet axis. Now, one can consider the yields as functions of phi_S phi_h integrated over phi_S or as functions of phi_S integrated over DeltaPhi, and decouple the two mechanisms when detector acceptance is under control.

----- Meeting Notes (6/20/13 14:57) -----upper half

Estimating Leak-through Systematic17Transverse-spin Jet Asymmetries - DrachenbergAcceptance inefficiencies can allow non-zero effects to leak through and distort desired observable

Quantify distortion by event-weighting unpolarized data yields and calculating resulting asymmetries

Reasonable acceptance + small observed asymmetries Small upper-limits on leak-through systematic

0.2 < zreco < 0.3Assuming 10% Sivers asymmetry

For 10%, upper-limit ~ 0.0021For 2%, upper-limit ~ 0.000417[Anselm]

if you need time, I would cut this, since the contribution is so small, also sides people will comment why you do 1D fits

Sivers Asymmetries18Transverse-spin Jet Asymmetries - DrachenbergNo sign of sizable azimuthal asymmetry in jet production at s = 500 GeVConsistent with expectation from inclusive jets, di-jets, and neutral pions at s = 200 GeVAsymmetries shown as function of particle-jet pTCorresponding parton-jet pT lower by 0.6-1.4 GeV/c

Horizontal errors include uncertainties from statistics, calorimeter gains, efficiencies, track momentum, and tracking efficiency

pT [GeV/c]

18----- Meeting Notes (9/26/13 11:10) -----specify p_T range on left-hand plotspecify eta range

Sivers Asymmetries19Transverse-spin Jet Asymmetries - DrachenbergMeasured asymmetries shown in -binsNo sign of sizable asymmetryAsymmetries shown as function of particle-jet pTCorresponding parton-jet pT lower by 0.6-1.4 GeV/c

Horizontal errors include uncertainties from statistics, calorimeter gains, efficiencies, track momentum, and tracking efficiency

pT [GeV/c]

19----- Meeting Notes (9/26/13 11:10) -----point out pseudorapidity rangescite theory prediction number

Collins Asymmetries20Transverse-spin Jet Asymmetries - Drachenberg

Increased gluonic subprocesses at s = 500 GeV lead to expectation of small Collins asymmetry until larger zPresent data do not have sufficient statistics at high-z to observe Collins asymmetry of order 1%DAlesio et al.20

Collins Asymmetries21Transverse-spin Jet Asymmetries - DrachenbergPresent model predictions expect negligible effects forAUT vs. jT integrated over z > 0.1Measured asymmetries shown for xF > 0 (i.e. 0 < jet < 1) in z-binsNo sign of non-zero asymmetry as a function of jT or jet pTSimilarly, no sign of positive effect for backward region (xF < 0), as expected21----- Meeting Notes (9/26/13 11:10) -----explain what is plotted!!!!point to where is particle-jet pT

Collins-like Asymmetries22Transverse-spin Jet Asymmetries - Drachenberg

Maximized contributionfor s = 500 GeVModel predictions shown for maximized effect, saturated to positivity boundUntil now, Collins-like asymmetries completely unconstrained Sensitive to linearly polarized gluonsDAlesio et al.22

Collins-like Asymmetries23Transverse-spin Jet Asymmetries - Drachenberg

Measured asymmetries shown for -1 < < 1 in z-binsConsistently below 2% maximum from modelDAlesio et al.23[Anselm]

mention (maybe verbally) connection between jT and k\perp----- Meeting Notes (9/26/13 11:10) -----highlight z-ranges

Collins-like Asymmetries24Transverse-spin Jet Asymmetries - DrachenbergSimilarly, no large effect observed as a function of jet pTMeasured asymmetries shown for -1 < < 1 in z-bins24Summary25Transverse-spin Jet Asymmetries - DrachenbergSTAR data from 2011 provide first measurements of transverse spin asymmetries for jet production at central pseudorapidity and s = 500 GeV25So, I hope this workshop has shown how transverse spin physics is an active field in our quest to understand proton spin structure.

STAR has been an active participant in the investigation of large asymmetries at forward pseudorapidity, including investigations in both the x_F and p_T depednence out to increasingly high p_T. Now, with the capability of investigating the effects of the event topology on A_N, showing signs that the largest asymmetries are found in the most isolated neutral pions. Furthermore, work is underway to investigate neutral-energy jets in our forward calorimeter at 500 GeV to bring this picture into even sharper focus. We have also, for the first time, measured neutral pion A_N at intermediate pseudorapidity, to extend our map of A_N as a function of x_F and p_T.

Also, we have seen that STAR is an active participant in investigation of transverse spin effects at more central pseudorapidity, where we use our full-jet reconstruction capability to probe for hints of transversity for the first time at larger values of x, acheivable at RHIC. We have seen signs of trasnversity also in our di-hadron asymmetries at mid-rapdidity. We have begun to extend these measurments at mid-rapdidity for the first time to 500 GeV, where one hopes to probe effects more sensensitive to gluonic production. And Run-12 datasets promise much greater precision than previous datasets at 200 GeV.

----- Meeting Notes (9/26/13 11:10) -----consistent with expectation fromdefine "central pseudorapidity range"Summary26Transverse-spin Jet Asymmetries - DrachenbergSTAR data from 2011 provide first measurements of transverse spin asymmetries for jet production at central pseudorapidity and s = 500 GeVIncreased gluonic subprocesses at s = 500 GeV provide unique sensitivity to Collins-like asymmetry from linearly polarized gluons26So, I hope this workshop has shown how transverse spin physics is an active field in our quest to understand proton spin structure.

STAR has been an active participant in the investigation of large asymmetries at forward pseudorapidity, including investigations in both the x_F and p_T depednence out to increasingly high p_T. Now, with the capability of investigating the effects of the event topology on A_N, showing signs that the largest asymmetries are found in the most isolated neutral pions. Furthermore, work is underway to investigate neutral-energy jets in our forward calorimeter at 500 GeV to bring this picture into even sharper focus. We have also, for the first time, measured neutral pion A_N at intermediate pseudorapidity, to extend our map of A_N as a function of x_F and p_T.

Also, we have seen that STAR is an active participant in investigation of transverse spin effects at more central pseudorapidity, where we use our full-jet reconstruction capability to probe for hints of transversity for the first time at larger values of x, acheivable at RHIC. We have seen signs of trasnversity also in our di-hadron asymmetries at mid-rapdidity. We have begun to extend these measurments at mid-rapdidity for the first time to 500 GeV, where one hopes to probe effects more sensensitive to gluonic production. And Run-12 datasets promise much greater precision than previous datasets at 200 GeV.

----- Meeting Notes (9/26/13 11:10) -----consistent with expectation fromdefine "central pseudorapidity range"Summary27Transverse-spin Jet Asymmetries - DrachenbergSTAR data from 2011 provide first measurements of transverse spin asymmetries for jet production at central pseudorapidity and s = 500 GeVIncreased gluonic subprocesses at s = 500 GeV provide unique sensitivity to Collins-like asymmetry from linearly polarized gluonsNo observation of large asymmetry from gluon Sivers effect, consistent with expectations from previous measurements of jet and 0 asymmetries at s = 200 GeV27So, I hope this workshop has shown how transverse spin physics is an active field in our quest to understand proton spin structure.

STAR has been an active participant in the investigation of large asymmetries at forward pseudorapidity, including investigations in both the x_F and p_T depednence out to increasingly high p_T. Now, with the capability of investigating the effects of the event topology on A_N, showing signs that the largest asymmetries are found in the most isolated neutral pions. Furthermore, work is underway to investigate neutral-energy jets in our forward calorimeter at 500 GeV to bring this picture into even sharper focus. We have also, for the first time, measured neutral pion A_N at intermediate pseudorapidity, to extend our map of A_N as a function of x_F and p_T.

Also, we have seen that STAR is an active participant in investigation of transverse spin effects at more central pseudorapidity, where we use our full-jet reconstruction capability to probe for hints of transversity for the first time at larger values of x, acheivable at RHIC. We have seen signs of trasnversity also in our di-hadron asymmetries at mid-rapdidity. We have begun to extend these measurments at mid-rapdidity for the first time to 500 GeV, where one hopes to probe effects more sensensitive to gluonic production. And Run-12 datasets promise much greater precision than previous datasets at 200 GeV.

----- Meeting Notes (9/26/13 11:10) -----consistent with expectation fromdefine "central pseudorapidity range"Summary28Transverse-spin Jet Asymmetries - DrachenbergSTAR data from 2011 provide first measurements of transverse spin asymmetries for jet production at central pseudorapidity and s = 500 GeVIncreased gluonic subprocesses at s = 500 GeV provide unique sensitivity to Collins-like asymmetry from linearly polarized gluonsNo observation of large asymmetry from gluon Sivers effect, consistent with expectations from previous measurements of jet and 0 asymmetries at s = 200 GeVNo observation of large asymmetry from Collins effect, consistent with expectations from decreased quark subprocesses at s = 500 GeV28So, I hope this workshop has shown how transverse spin physics is an active field in our quest to understand proton spin structure.

STAR has been an active participant in the investigation of large asymmetries at forward pseudorapidity, including investigations in both the x_F and p_T depednence out to increasingly high p_T. Now, with the capability of investigating the effects of the event topology on A_N, showing signs that the largest asymmetries are found in the most isolated neutral pions. Furthermore, work is underway to investigate neutral-energy jets in our forward calorimeter at 500 GeV to bring this picture into even sharper focus. We have also, for the first time, measured neutral pion A_N at intermediate pseudorapidity, to extend our map of A_N as a function of x_F and p_T.

Also, we have seen that STAR is an active participant in investigation of transverse spin effects at more central pseudorapidity, where we use our full-jet reconstruction capability to probe for hints of transversity for the first time at larger values of x, acheivable at RHIC. We have seen signs of trasnversity also in our di-hadron asymmetries at mid-rapdidity. We have begun to extend these measurments at mid-rapdidity for the first time to 500 GeV, where one hopes to probe effects more sensensitive to gluonic production. And Run-12 datasets promise much greater precision than previous datasets at 200 GeV.

----- Meeting Notes (9/26/13 11:10) -----consistent with expectation fromdefine "central pseudorapidity range"Summary29Transverse-spin Jet Asymmetries - DrachenbergSTAR data from 2011 provide first measurements of transverse spin asymmetries for jet production at central pseudorapidity and s = 500 GeVIncreased gluonic subprocesses at s = 500 GeV provide unique sensitivity to Collins-like asymmetry from linearly polarized gluonsNo observation of large asymmetry from gluon Sivers effect, consistent with expectations from previous measurements of jet and 0 asymmetries at s = 200 GeVNo observation of large asymmetry from Collins effect, consistent with expectations from decreased quark subprocesses at s = 500 GeVFirst measurements of Collins-like asymmetries will help place constraints on model predictions beyond maximal projections from positivity bounds29So, I hope this workshop has shown how transverse spin physics is an active field in our quest to understand proton spin structure.

STAR has been an active participant in the investigation of large asymmetries at forward pseudorapidity, including investigations in both the x_F and p_T depednence out to increasingly high p_T. Now, with the capability of investigating the effects of the event topology on A_N, showing signs that the largest asymmetries are found in the most isolated neutral pions. Furthermore, work is underway to investigate neutral-energy jets in our forward calorimeter at 500 GeV to bring this picture into even sharper focus. We have also, for the first time, measured neutral pion A_N at intermediate pseudorapidity, to extend our map of A_N as a function of x_F and p_T.

Also, we have seen that STAR is an active participant in investigation of transverse spin effects at more central pseudorapidity, where we use our full-jet reconstruction capability to probe for hints of transversity for the first time at larger values of x, acheivable at RHIC. We have seen signs of trasnversity also in our di-hadron asymmetries at mid-rapdidity. We have begun to extend these measurments at mid-rapdidity for the first time to 500 GeV, where one hopes to probe effects more sensensitive to gluonic production. And Run-12 datasets promise much greater precision than previous datasets at 200 GeV.

----- Meeting Notes (9/26/13 11:10) -----consistent with expectation fromdefine "central pseudorapidity range"Looking Forward30Transverse-spin Jet Asymmetries - DrachenbergAdditional data from 2011 jet-patch triggers will allow much greater precision for higher jet pT (above 7 GeV/c)High precision measurements from 2012 at s = 200 GeV will allow greater sensitivity to effects from quark subprocesses

STAR Preliminary Results at s = 500 GeVSivers AsymmetriesCollins AsymmetriesCollins-like Asymmetries30So, I hope this workshop has shown how transverse spin physics is an active field in our quest to understand proton spin structure.

STAR has been an active participant in the investigation of large asymmetries at forward pseudorapidity, including investigations in both the x_F and p_T depednence out to increasingly high p_T. Now, with the capability of investigating the effects of the event topology on A_N, showing signs that the largest asymmetries are found in the most isolated neutral pions. Furthermore, work is underway to investigate neutral-energy jets in our forward calorimeter at 500 GeV to bring this picture into even sharper focus. We have also, for the first time, measured neutral pion A_N at intermediate pseudorapidity, to extend our map of A_N as a function of x_F and p_T.

Also, we have seen that STAR is an active participant in investigation of transverse spin effects at more central pseudorapidity, where we use our full-jet reconstruction capability to probe for hints of transversity for the first time at larger values of x, acheivable at RHIC. We have seen signs of trasnversity also in our di-hadron asymmetries at mid-rapdidity. We have begun to extend these measurments at mid-rapdidity for the first time to 500 GeV, where one hopes to probe effects more sensensitive to gluonic production. And Run-12 datasets promise much greater precision than previous datasets at 200 GeV.