1/18
Sea Quark Longitudinal Spin: measurements at PHENIXDaniel Jumper
University of Illinois at Urbana-Champaign
For the PHENIX collaboration
CIPANP – Vail, CO – May 23, 2015 Proton Longitudinal Spin Structure Boson Probe for Polarized at RHIC PHENIX Measurements:
2/18
Danie
l Jum
per - P
HE
NIX
W P
hysics
Proton Spin Spin Composition of the Proton:
– Quark and anti quark spins
– Gluon spin
orbital angular momentum
Current Understanding DIS/SIDIS
some flavor separation
RHIC
and , with separation
5/2
3/2
01
5
3/18
Danie
l Jum
per - P
HE
NIX
W P
hysics
Accessing Sea Quark Spin
Advantages over DIS/SIDIS No fragmentation
functions
High
Constraints: Weak parity violation
’s couple to left handed and right handed
Known spin distributions
spin tends to be aligned with proton spin, anti-aligned
𝑊 ±
5/2
3/2
01
5
4/18
Danie
l Jum
per - P
HE
NIX
W P
hysics
Flavor Sensitivity at Forward Rapidity
A first order motivation: At large rapidity or
equations reduce:
Actual observable:
This and other higher order effects are accounted for in global fit
Proton Constituent Probability Distributions
5/2
3/2
01
5
5/18
Danie
l Jum
per - P
HE
NIX
W P
hysics
Spin at RHIC at up to 60% polarization
“Siberian Snake” Spin Flippers
5/2
3/2
01
5
6/18
Danie
l Jum
per - P
HE
NIX
W P
hysics
Spin at RHIC
Runs 2011-2013 2013 offers highest
luminosity
High polarization is important for figure of merit
5/2
3/2
01
5
7/18
Danie
l Jum
per - P
HE
NIX
W P
hysics
PHENIX W Measurements
Central
Forward
5/2
3/2
01
5
8/18
Danie
l Jum
per - P
HE
NIX
W P
hysics
Central
Forward
PHENIX W Measurements5
/23
/20
15
9/18
Danie
l Jum
per - P
HE
NIX
W P
hysics
Central
Forward
PHENIX W Measurements5
/23
/20
15
10/18
Danie
l Jum
per - P
HE
NIX
W P
hysics
Central
Analysis Strategy: Reduce Background with
Relative Isolation Cut Energy ratio between candidate
and all hits in a cone
Factor of 10 reduction in Bkg
Fit Jacobian Peak Extrapolate background with Gaussian Process Regression technique
Fit signal + bkg model to data to extract signal yield
Calculate Asymmetry
5/2
3/2
01
5
11/18
Danie
l Jum
per - P
HE
NIX
W P
hysics
Central Run 13 final result just released!
Now available on arXiv: http://arxiv.org/pdf/1504.07451v1.pdf
5/2
3/2
01
5
12/18
Danie
l Jum
per - P
HE
NIX
W P
hysics
Forward 5
/23
/20
15
Challenge: Low signal with dominant background
13/18
Danie
l Jum
per - P
HE
NIX
W P
hysics
Forward
Challenge: Low signal with dominant background
Signal events dominated by other processes at low
Process cross sections vs from simulations
5/2
3/2
01
5
14/18
Danie
l Jum
per - P
HE
NIX
W P
hysics
Forward
Challenge: Low signal with dominant background
Signal events dominated by other processes at low
Limited resolution smears dominant low background
Process cross sections vs from simulations
5/2
3/2
01
5
15/18
Danie
l Jum
per - P
HE
NIX
W P
hysics
Forward
Challenge: Low signal with dominant background
Signal events dominated by other processes at low
Limited resolution smears dominant low background
Additional “fake muons” result from multiple scattering hadronsProcess cross sections vs from simulations
5/2
3/2
01
5
16/18
Danie
l Jum
per - P
HE
NIX
W P
hysics
Forward Analysis Strategy: Select High-Signal Data Subset
Multivariate Likelihood Ratio Calculation
Characterize Remaining Data Signal to Background Ratio Fit
Use simulations to estimate
distributions for components
Calculate & Correct Asymmetry Count yields for each helicity
Apply correction factors (Sig/Bkg ratio, efficiencies, …)
Likelihood Ratio
BackgroundSignal
SigBkg
5/2
3/2
01
5
17/18
Danie
l Jum
per - P
HE
NIX
W P
hysics
Forward
Preliminary Result
Currently moving toward a finalized result and publication
5/2
3/2
01
5
18/18
Danie
l Jum
per - P
HE
NIX
W P
hysics
Summary
Proton spin structure remains poorly constrained
’s as a weak probe, offer unique insight to ,
Forthcoming PHENIX results contribute to significantly improved constraints on these distributions Central results just released
Forward preliminary result available
5/2
3/2
01
5
19/18
Danie
l Jum
per - P
HE
NIX
W P
hysics
Backup
5/2
3/2
01
5
Top Related