Heavy Flavor and Spin

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Heavy Flavor and Spin

• Ernst Sichtermann

Heavy Flavor Workshop, Berkeley - October 2005
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Nucleon Spin - Questions
The Quark-Parton Model fits the Baryon Zoo, and
describes the gross features of the proton
sub-structure (Bjorken Scaling, ...), Yet,
gluons carry half the protons momentum, the
naive QPM fails miserably in describing the
protons spin structure (EMC - 1988)
The role of RHIC-spin
What is the role of the gluon spin? Which
symmetries are at play?
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RHIC Spin - Present
0.5 pb-1, 40 pol
Joanna Kiryluk - Thursday Oct 13
Inclusive Jets
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RHIC Spin - Present
The start of beautiful measurements, hard
scale and fair kinematic coverage,
fragmentation uncertainties enter only through
trigger and reconstruction bias, -
contributions from qg and gg scattering, which
are not resolved, - ALL(pT)
?
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RHIC Spin - (Far) Future
320 800 pb-1, 70 pol
Prompt-photon Jet coincidences
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RHIC Spin - Future
0.5 pb-1 to 320800 pb-1... Dijet measurements
help resolve kinematics, but are of rather
limited use in separating qg and gg
contributions, Heavy flavor singles out the
gluons, Heavy flavor dijets?
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RHIC Spin - Experiment Demands
STAR measures asymmetries for different spin
states, e.g. and their relative
luminosity, RHIC measures the polarization.
100ns between bunches
Original HFT proposal what use may the device
have for SPIN?
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HFT and Spin Need for Some Speed...,

Fast-MC - two H.F.T. layers 30µm
pixels, 15 and 40 mm radii, - one faster
detector layer 300µm pixels,
100mm radius, 10-100 times faster, -
tracking starts from H.F.T., - somewhat naive
vertexing, - multiple scattering, digitization,
- /- 20 cm beam diamond, - no magnetic field,
... Here, signal stands for displaced (e,h) pair
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HFT and Spin Baseline Measurement

100 pb-1, 70 pol
SVT adequate intrinsic speed, inadequate rate
capability, NLO framework exists (Bojak and
Stratmann), Transverse baseline gluon Sivers
function
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Discussion Starters Partonic Asymmetry
Partonic asymmetry depends at lowest order on the
heavy quark mass in a dramatic way. This should
be measurable, unless is vanishingly small
or the yields of (trigger-) electrons from charm
and beauty are very different at 5 GeV/c
charm - continuous curves, beauty - dotted curves
Either way, this seems a fruitful ground to
test/learn about pQCD.
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Discussion Starters - possible or not?
- - B.R.s small, e.g.
1 large, good polarimeter! This
might open new measurements for spin,
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which all relate to in a way that does not
depend on relative luminosity (and any ALL its
measurement might exhibit!) K. Sudoh, V. Rykov.
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Discussion Starters 500 GeV and Beyond?
Standard 500 GeV
See Bernds talk
resolves (anti-)up and down quark
polarization. That is, strange quark polarization
is likely to remain mostly unknown. Can STAR
measure (in the RHIC-II era) and is it
sensitive (enough) to ?
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Discussion Starters 500 GeV and Beyond?
First estimates now exist (and confirm earlier
thoughts of 5 fb-1 luminosity needs).
K. Sudoh
It is not evident (to me) that the charm
acceptance is matched (homework).
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HFT / IST
Slow HFT alone has very limited spin physics
purposes, Inclusive electron spin measurements
feasible, Electron correlations statistically
challenged, IST / HFT heavy quark dijets and
charm/beauty separation, Strange quark
polarization is likely beyond our scope