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Inclusive J/ Longitudinal Double Spin Asymmetry Measurements at Forward Rapidity in p+p Collisions at PHENIX Haiwang Yu (Peking University) for PHENIX Collaboration The 7th International Workshop on Charm Physics (CHARM 2015) Wayne State

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SLIDE 1

Inclusive J/ψ Longitudinal Double Spin Asymmetry Measurements at Forward Rapidity in p+p Collisions at PHENIX

Haiwang Yu (Peking University) for PHENIX Collaboration

The 7th International Workshop on Charm Physics (CHARM 2015) Wayne State University, Detroit, Michigan May 18-22, 2015.

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SLIDE 2

Outline

  • Proton Spin Structure
  • Gluon polarization of the RHIC Spin Program
  • 𝐾/πœ” double longitudinal asymmetry (𝐡𝑀𝑀) at forward

rapidity

Haiwang Yu, CHARM 2015 2

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SLIDE 3

Proton Spin Structure

"Spin Puzzle"

Haiwang Yu, CHARM 2015 3

Decomposition of the Proton Spin Manohar-Jaffe sum rule: π‘‡π‘ž = 1 2 = 1 2 ΔΣ + Δ𝐻 + π‘€π‘Ÿ + 𝑀𝑕 In 1980’s experiment by the European Muon Collaboration (EMC) discovered that quarks

  • nly carry a small portion of the proton spin.

Current knowledge from Polarized Deep Inelastic Scattering (DIS) and Semi-inclusive DIS (SIDIS) Measurements: ΔΣ = ~30%

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SLIDE 4

Proton Spin Structure

"Spin Puzzle"

Haiwang Yu, CHARM 2015 4

Decomposition of the Proton Spin Manohar-Jaffe sum rule: π‘‡π‘ž = 1 2 = 1 2 ΔΣ + Δ𝐻 + π‘€π‘Ÿ + 𝑀𝑕 In 1980’s experiment by the European Muon Collaboration (EMC) discovered that quarks

  • nly carry a small portion of the proton spin.

Current knowledge from Polarized Deep Inelastic Scattering (DIS) and Semi-inclusive DIS (SIDIS) Measurements: ΔΣ = ~30% Focus on this part today

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SLIDE 5

RHIC Spin Program

Gluon polarization

Haiwang Yu, CHARM 2015 5

2014 DSSV Global Fit

  • Including 2009 RHIC data sets, the 2014

DSSV global fit suggests non zero polarization of gluons in the proton at intermediate x range (0.05~0.2).

  • Yet at low x range, the errors of DSSV are

still poorly constrained

  • Measurements from forward rapidity

needed.

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SLIDE 6

RHIC Spin Program

World's only polarized proton collider

Haiwang Yu, CHARM 2015 6

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SLIDE 7

Double Longitudinal Asymmetry

Theoretically: 𝐡𝑀𝑀 = 𝜏++ βˆ’ 𝜏+βˆ’ 𝜏++ + 𝜏+βˆ’ = 𝑏,𝑐,𝑑=π‘Ÿ,

π‘Ÿ,𝑕 Δ𝑔 𝑏⨂Δ𝑔 𝑐⨂Δ

πœβ¨‚πΈβ„Ž/𝑑 𝑏,𝑐,𝑑=π‘Ÿ,

π‘Ÿ,𝑕 𝑔 𝑏⨂𝑔 𝑐⨂

πœβ¨‚πΈβ„Ž/𝑑 Experimentally: 𝐡𝑀𝑀 = 1 𝑄𝐢𝑄𝑍 𝑂++ βˆ’ 𝑆 𝑂+βˆ’ 𝑂++ + 𝑆𝑂+βˆ’ Where 𝑄𝐢,𝑍 is the polarization of Blue (Yellow) beam. And R is the relative luminosity: 𝑆 = 𝑀++ 𝑀+βˆ’

Haiwang Yu, CHARM 2015 7

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SLIDE 8

RHIC Spin Program

Recent Longitudinal Runs

PHENIX Recent Longitudinal Runs: Figure of Merit:

High polarization is essential for effective asymmetry measurement: Single Spin Asymmetry: 𝑀 < 𝑄 >2 Double Spin Asymmetry: 𝑀 < 𝑄 >4 Haiwang Yu, CHARM 2015 8

Year 𝑑(GeV) L(π‘„π‘βˆ’1) P(%) FoM(𝑄4𝑀) 2003 200 0.35 27 0.0019 2004 200 0.12 40 0.0031 2005 200 3.4 49 0.2 2006 200 7.5 57 0.79 2006 62.4 0.08 48 0.0042 2009 500 10 40 0.26 2009 200 14 57 1.4 2011 500 16.7 48 0.88 2012 510 30.03 52 2.2 2013 510 150 55 14

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SLIDE 9

Haiwang Yu, CHARM 2015 9

𝜈+ πœˆβˆ’

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𝐾/πœ” 𝐡𝑀𝑀 @ forward rapidity

J/ψ production at RHIC

Haiwang Yu, CHARM 2015 10

  • Phys. Rev. D56 (1997) 7341

At RHIC energies 𝐾/πœ” production is dominated by gluon-gluon fusion. The 𝐡𝑀𝑀 for 𝐾/πœ” can be written (LO): 𝐡𝑀𝑀 = Ξ”πœ 𝜏 ∝ Δ𝑕(𝑦1) 𝑕(𝑦1) Δ𝑕(𝑦2) 𝑕(𝑦2)

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SLIDE 11

𝐾/πœ” 𝐡𝑀𝑀 @ forward rapidity

Bjorken x range

Benefits of Forward Rapidity

  • At forward rapidity the x distributions of

the two gluons are at very different region

  • Instead of probing ~ Δ𝑕/𝑕 2 we are

probing

Δ𝑕(𝑦1) 𝑕(𝑦1) Δ𝑕(𝑦2) 𝑕(𝑦2)

  • High-x gluon sits in the x-range where RHIC

Run9 data already has constraints on the Δ𝑕

  • Therefore, this forward 𝐾/πœ” β†’ 𝜈+πœˆβˆ’ 𝐡𝑀𝑀

gives sensitivity to possible sign change in Δ𝑕 and cleanly accesses down to 𝑦 ~ 2 Γ— 10βˆ’3

Haiwang Yu, CHARM 2015 11

from Pythia simulation

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SLIDE 12

𝐾/πœ” 𝐡𝑀𝑀 @ forward rapidity

Excited states feed-down

Haiwang Yu, CHARM 2015 12

Charmonium

  • Except for 𝐾/πœ”'s, excited charmonium states

are also generated in RHIC p+p collisions

  • πœ“π‘‘ and πœ”β€² feed-down forms a sizable portion
  • Phys. Rev. D 85, 092004 (2012)
  • πœ”β€² overlaps with 𝐾/πœ”
  • Different calculating schemes gave different Ξ”g

depends for each excited states (Phys. Rev. D 56, 7341 (1997))

  • Good test bed for different aspects of NRQCD

factorization and scaling

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SLIDE 13
  • Vertex selection: |BBC_Z|<30 cm
  • common PHENIX muon tracks quality

cuts including:

  • from same arm
  • track matching between muon tracker and

identifier

  • penetrating muon candidates cuts
  • etc.
  • RPC timing cut are applied to guarantee

𝐾/πœ”'s are from the right bunch crossing

𝐾/πœ” 𝐡𝑀𝑀 @ forward rapidity

Event and track selection

Haiwang Yu, CHARM 2015 13 𝜈+πœˆβˆ’ inv. mass spectrum after event and 𝜈 track selection sideband region is used to estimate background asymmetry 𝜍, πœ•, 𝜚 𝐾/πœ”, πœ”β€²

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SLIDE 14

Sideband

𝐾/πœ” 𝐡𝑀𝑀 @ forward rapidity

measurement procedure

Outline

  • Analyze south and north arm separately, and divide

data from each arm into 3 π‘žπ‘ˆ bins. So 6 subsets total.

  • Fit each subsets for 2𝜏 J/ψ mass window and

background fraction "r".

  • CB shape for J/ψ, Gaussian for ψ'
  • Gaussian Process Regression (GPR) for background shape
  • Sideband region is defined as π‘πœˆπœˆ ∈ [1.5π»π‘“π‘Š, 2.5π»π‘“π‘Š]
  • Calculate 𝐡𝑀𝑀

π‘—π‘œπ‘‘π‘š. in the 2𝜏 J/ψ mass window

  • Estimate the background asymmetry from a sideband

𝐡𝑀𝑀

𝐾/πœ” = 𝐡𝑀𝑀 π‘—π‘œπ‘‘π‘š. βˆ’ 𝑠 βˆ— 𝐡𝑀𝑀 𝐢𝐿𝐻.

1 βˆ’ 𝑠 Δ𝐡𝑀𝑀

𝐾/πœ” =

(Δ𝐡𝑀𝑀

π‘—π‘œπ‘‘π‘š.)2 + 𝑠2 βˆ— (Δ𝐡𝑀𝑀 𝐢𝐿𝐻.)2

1 βˆ’ 𝑠

Haiwang Yu, CHARM 2015 14 Gaussian Process Regression (GPR) background fraction extraction

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SLIDE 15

𝐾/πœ” 𝐡𝑀𝑀 @ forward rapidity

recent results

Haiwang Yu, CHARM 2015 15

π‘žπ‘ž β†’ 𝐾/πœ” + X β†’ 𝜈+ + πœˆβˆ’ + π‘Œ @ 𝑑 = 200π»π‘“π‘Š π‘žπ‘ž β†’ 𝐾/πœ” + X β†’ 𝜈+ + πœˆβˆ’ + π‘Œ @ 𝑑 = 510π»π‘“π‘Š

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SLIDE 16

Summary & outlook

  • Including data from RHIC spin program, the recent DSSV global

analysis indicates non-zero Δ𝐻 for x larger than 0.05.

  • We measured the 𝐾/πœ” 𝐡𝑀𝑀 for 200GeV and 510GeV at forward

rapidity which provides access to the small-x region (~10-3)

  • We encourage theory community to incorporate this data in

future NLO fits.

  • The 𝐾/πœ” cross-section measurement @ 510 GeV is undergoing.

Haiwang Yu, CHARM 2015 16

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SLIDE 17

Backup slides

Haiwang Yu, CHARM 2015 17

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SLIDE 18

𝐾/πœ” production vs. rapidity at 200GeV

Haiwang Yu, CHARM 2015 18

Phys.Rev.Lett.98:232002,2007

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SLIDE 19

PHENIX 2013 pi0 𝐡𝑀𝑀 Measurement

Haiwang Yu, CHARM 2015 19

  • H. Guragain, DIS 2015
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SLIDE 20

Star 2009 Inclusive Jet 𝐡𝑀𝑀 Measurement

Haiwang Yu, CHARM 2015 20

arXiv:1303.0543

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SLIDE 21

PHENIX 2009 𝜌0 𝐡𝑀𝑀 Measurement

Haiwang Yu, CHARM 2015 21

arXiv:1402.6296.

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𝐾/πœ” 𝐡𝑀𝑀 @ forward rapidity

Systematic uncertainty

  • Background fraction "r", using different

fitting method:

  • Gaussian Progress Regression
  • Simulation driven
  • Polynomial background etc.
  • Different run clustering:
  • Luminosity and trigger eff. based clustering

using mean shift algorithm

  • Fill-by-fill clustering
  • Sum all runs in one group
  • Asymmetry from relative luminosity

measurement

Haiwang Yu, CHARM 2015 22

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SLIDE 23

Haiwang Yu, CHARM 2015 23

𝐾/πœ” 𝐡𝑀𝑀 result for North and South Muon arm separately

result based on 2013 RHIC 500GeV p+p run data set

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SLIDE 24

bunch shuffling

The fact that the normalized RMS close to 1, indicates that all other non correlated bunch-to-bunch and fill-to-fill systematic errors are much smaller than the statistical errors.

Haiwang Yu, CHARM 2015 24

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SLIDE 25

Haiwang Yu, CHARM 2015 25

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SLIDE 26

Ground and excited state charmonium production in p+p collisions at √s=200 GeV

Haiwang Yu, CHARM 2015 26

  • Phys. Rev. D 85

85, 092004 (2012)

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SLIDE 27

Haiwang Yu, CHARM 2015 27

Systematics Uncertainty from run clustering

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SLIDE 28

background fraction "r"

The extraction of "r" has been done using several methods: GPR for the background, simulation driven, and the old fashion polynomial. At the end, we took the GPR method as the central value and the difference as

  • ne systematic error.

showing different fitting methods Showing one arm, one pT bin fitting for the Final result

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SLIDE 29

Haiwang Yu, CHARM 2015 29

Systematics Uncertainty from background fraction extraction

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background Asymmetry ry 𝐡𝑀𝑀

𝐢𝐿𝐻. Estimation

  • We try to justify there is no obvious mass dependence of the asymmetry of the side

band beyond the stat. err. can tell. So as we already assigned relatively large stat. err. to the background asymmetry, we ignored the sys. err. from this estimation method.

  • AN1194 Figure 9:
  • showing the side-band asymmetry for different mass window
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SLIDE 31

if use this very conservative sys. err. from side band estimation method:

31 Haiwang Yu, CHARM 2015

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SLIDE 32

Haiwang Yu, CHARM 2015 32

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SLIDE 33

New global Fitting

2014 DSSV Global Fit

33

  • Phys. Rev. Lett. 113, 012001 (2014)

Haiwang Yu, CHARM 2015

  • Including 2009 RHIC data sets, the 2014 DSSV global fit suggests non zero polarization of

gluons in the proton at intermediate x range (0.05~1).

  • Yet at low x range, the errors of DSSV are still poorly constrained
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SLIDE 34

Recent Results

Global Fit: DSSV++

Haiwang Yu, CHARM 2015 34

Outlook:

  • Large uncertainties remain in both the shape and integral of βˆ†g(x)
  • Unconstrained in the low x range where currently no data is available
  • Improvements forthcoming from ALL measurements at 510 GeV and

forward rapidity

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SLIDE 35

Proton Spin Structure

"Spin Puzzle"

Haiwang Yu, CHARM 2015 35

Decomposition of the Proton Spin Manohar-Jaffe sum rule: π‘‡π‘ž = 1 2 = 1 2 ΔΣ + Δ𝐻 + π‘€π‘Ÿ + 𝑀𝑕 In 1980’s experiment by the European Muon Collaboration (EMC) discovered that quarks

  • nly carry a small portion of the proton spin.

Current knowledge from Polarized Deep Inelastic Scattering (DIS) and Semi-inclusive DIS (SIDIS) Measurements: ΔΣ = ~30%

  • Phys. Lett. B206 364
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SLIDE 36

RHIC Spin Program

Gluon and sea quark polarization

Haiwang Yu, CHARM 2015 36

Current status:

  • Gluon polarization is largely

unconstrained

  • Large uncertainty in fragmentation

functions leads to large uncertainty on sea quark polarization Access Δ𝐻(𝑦) @ LO:

  • PHENIX 𝜌0 measurements
  • PHENIX 𝐾/πœ” measurements
  • Star inclusive Jet measurements

Sea quark polarization Measurement

  • 𝑋 measurements in lepton channel
  • Phys. Rev. D 80, 034030 (2009)
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SLIDE 37

RHIC Spin Program

World's only polarized proton collider

Haiwang Yu, CHARM 2015 37