lecture i&ii rhic the relativistic heavy ion collider
TRANSCRIPT
Lecture I&IILecture I&IIRHICRHIC
The Relativistic Heavy Ion The Relativistic Heavy Ion ColliderCollider
Particle acceleratorsParticle accelerators
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Large scientific instruments that produce and accelerate subatomic particles and ‘smashes them’
Fixed target
Collider
Particles: electrons, positrons, protons, anti-protons, ions…..(atoms stripped of electrons: nuclei)
Nuclei protons + neutrons quarks + gluons
RHIC @ Brookhaven National Lab RHIC @ Brookhaven National Lab
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RHIC
NSRLLINAC
Booster
AGS
Tandems
STAR6:00 o’clock
PHENIX8:00 o’clock
Jet/C-Polarimeters12:00 o’clock
RF4:00 o’clock
EBIS
ERL Test Facility
ANDY2:00 o’clock
What do we collide ?
p
Polarized light ions He3 16 - 166 GeV/u
Light ions (d,Si,Cu)Heavy ions (Au,U)5-100 GeV/u
Polarized protons24-250 GeV
1st Collisions: 13/06/2000
STAR
PHENIX
AGS
LINACBOOSTER
Pol. Proton Source500 A, 300 s
Spin Rotators
Partial Siberian Snake
Siberian Snakes
200 MeV Polarimeter AGS Internal Polarimeter
Rf Dipoles
RHIC pC PolarimetersAbsolute Polarimeter (H jet)
AGS pC Polarimeters
Strong AGS Snake
MP6 MP7
Tandem Van der Graaf
Stripping Au 77+ to 79+
1 MeV/u32+
9 GeV/u77+
100 GeV/u79+
The RHIC ComplexThe RHIC Complex
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ANDY
BoosterRing
AGS
Switchyard
RHIC
TandemVan de Graaff
The RHIC Accelerator SystemThe RHIC Accelerator System
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Blue Ring
Yellow Ring
What does RHIC do?What does RHIC do?
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RHIC accelerates gold nuclei in two
beams to about 100 GeV/nucleon each
(i.e., to kinetic energies that are over
100 times their rest mass-energy)and brings these beams into a200 GeV/nucleon collision.
RHIC accelerates polarized protonsup to 250 GeV and brings them intoup to 500 GeV collision
Three experiments, STAR,PHENIX, and ANDY study these collisions.
The RHIC project chronologyThe RHIC project chronology
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1989 RHIC design 1991 construction starts 1996 commissioning AtR injection lines 1997 sextant test (1/6 of the ring) 1999 RHIC engineering/test run 2000 first collisions 2001-02 Au-Au run, polarized p run 2003 deuteron-Au run, pp 2004 Au-Au physics run and 5 weeks pp development 2005 …..RHIC is also a giant engineering challenge: magnets (3000+ industry and lab built superconducting
magnets)cryogenics (2 weeks to cool down to
4.2K) ,instrumentation, etc.
RHIC operationsRHIC operations
The operation of RHIC and its injectors is a rather challenging endeavor….
RHIC operates for ~5-6 months/year – 24h/day 7 days/weekRHIC Shutdown 6-7 months, for machine improvements (other
programs are run by the injectors, Tandem delivering ions for industrial R&D, Booster delivering ions for NASA experiments, etc.)
CONTROL ROOM : remote access to instrumentations and controls
Accelerator physicists, shift leaders (machine initial set-up, new developments, beam experiments)
Operations group: operation coordinator, operators (“routine’ operations, shifts 1 OC + 2 operators)
Technical support (engineers and technicians on call and/or site for system diagnosis and trouble-shooting)
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Beamintensities
Pilotbunch
injection
accelerationpreparation
collisionsSet-up
Store(collisions)
time
Startacceleration
transition
Beta*squeeze
coggingre-bucketingcollimationsteering
collisions
inject, accelerate, collide......!inject, accelerate, collide......!
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A day in the life of RHIC…A day in the life of RHIC…
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designluminosity
Week 9 Feb to 17 Feb [66% of calendar time in store]
enhancedluminosity
60x109Auintensity
Beam
exp
eri
men
ts
A week in the life of RHIC…A week in the life of RHIC…
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A few years in the life of RHIC…A few years in the life of RHIC…
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Polarized proton runs
Operated modes (beam energies):Au–Au 3.8/4.6/5.8/10/14/32/65/100 GeV/nd–Au* 100 GeV/n Cu–Cu 11/31/100 GeV/np–p 11/31/100, 250 GeV Planned or possible future modes:Au – Au 2.5 GeV/n (~ SPS cm energy)U – U 100 GeV/np – Au* 100 GeV/nCu – Au* 100 GeV/n (*asymmetric rigidity)
Achieved peak luminosities (100 GeV, nucl.-pair):Au–Au 1951030 cm-2 s -1
p–p 601030 cm-2 s -1
Other large hadron colliders (scaled to 100 GeV):Tevatron (p – pbar) 431030 cm-2 s -1
LHC (p – p) 371030 cm-2 s -1
AAnnDY in Run-11 (250 GeV pp)DY in Run-11 (250 GeV pp)
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Beam envelope function * = 3.0 m at IP2 Reduced IP2 crossing angle from initially 2.0 mrad to zero Added 3rd collision with following criteria (last instruction):
ü Nb ≤ 1.5x1011
ü Beam loss rate <15%/h in both beamsü Not before first polarization measurement 3h into store
PHENIX
STAR
AnDY
small impact visible impact,few percent loss to STAR/PHENIX
loss rates
/IP = 0.004
/IP = 0.005
13
AANNDY an getting LumiDY an getting Lumi
14
~2mr crossing angle
~1.6mr crossing angle
~0mr crossing angle
systematically increased thresholds
for IP2 collisions
ANDY got ~ 6.5/pb
in run11 with *=3m
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Future operation of AFuture operation of AnnDY DY
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Can reduce * at IP2have run with * = 2.0 m previously for BRAHMS* = 1.5 m probably ok, needs to be tested
Longer stores 10h instead of 8h in Run-11 (depends on luminosity lifetime and
store-to-store time) Collide earlier in store when conditions are met
needs coordination with polarization measurement, PHENIX and STAR
Electron lenses (see later) if AnDY runs beyond Run-13 increases max beam-beam tune spread, currently Qmax,bb ≈ 0.015 can be used for to increase ~Nb/ and/or number of collisions
Run-11 luminosity at AnDY: max ~0.5 pb-1/store
With improvements: ~3x increase, ~10 pb-1/week (max)
15
pp in Run-4 (100 GeV)
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What is Spin? From Google…What is Spin? From Google…
revolve quickly and repeatedly around one's own axis, "The dervishes whirl around and around without getting dizzy”
twist and turn so as to give an intended interpretation, "The President's spokesmen had to spin the story to make it less embarrassing”
a distinctive interpretation (especially as used by politicians to sway public opinion), "the campaign put a favorable spin on the story"
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What is Spin?What is Spin?
Classical definition the body rotation around its own axis
Particle spin: an intrinsic property, like mass and charge a quantum degree freedom associated with the intrinsic
magnetic moment.
G: anomalous gyromagnetic factor, describes the particle internal structure. For particles:
point-like: G=0 electron: G=0.00115965219 muon: G=0.001165923 proton: G=1.7928474
m: particle mass
q: electrical charge of particle
s=(1 + G)
q
mS
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Spin: single particle pure spin state aligned along a quantization axis
Spin vector S: a collection of particles the average of each particles spin expectation value along a given direction
spin vector and spin-orbit interactionspin vector and spin-orbit interaction
BμdtSd
s
S
N
Spin orbit interaction
N
I IAμ
S
BμdtJd
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Figure of merit of polarized proton Figure of merit of polarized proton collidercollider
Luminosity: number of particles per unit area per unit
time. The higher the luminosity, the higher the collision
rates
beam polarization Statistical average of all the spin vectors.
zero polarization: spin vectors point to all directions. 100% polarization: beam is fully polarized if all spin
vectors point to the same directions.
)(
)(
4
1)(
2
2
0 t
tnNftL
rms
Transverse beam size
# of particles in one bunch
# of bunches
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Basics of circular acceleratorBasics of circular accelerator
bending dipole Constant magnetic field Keeps particles circulating around the ring
quadrupole Magnetic field proportional to the distance from the
center of the magnet. Keeps particles focused
radio frequency cavities Electric field for acceleration and keeping beam
bunched longitudinally
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Closed orbit in a machine with dipole errors
Closed orbit ina perfect machine:center of quadrupoles
Closed orbit: particle comes back to the same position after one orbital revolution
Closed orbit in a circular acceleratorClosed orbit in a circular accelerator
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))(2cos(2)( yyy sQJsy Beta function
Betatron tune: number of oscillations in one orbital revolution
Betatron oscillation in a circular Betatron oscillation in a circular acceleratoraccelerator
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Spin motion in circular accelerator:Spin motion in circular accelerator: Thomas BMT Equation Thomas BMT Equation
In a perfect accelerator, spin vector precesses around the bending dipole field direction: vertical
Spin tune Qs: number of precessions in one orbital revolution. In general,
SBGBGm
eS
dt
Sd
])1([ //
€
Qs = Gγ
Spin vector in particle’s rest frame
B
beam
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polarized proton acceleration polarized proton acceleration challenges:challenges:
preserve beam polarization preserve beam polarization Depolarization (polarization loss) mechanism
Come from the horizontal magnetic field which kicks the spin vector away from its vertical direction
Spin depolarizing resonance : coherent build-up of perturbations on the spin vector when the spin vector gets kicked at the same frequency as its precession frequency
xB
x
y
z
beam
Initial
xB
x
y
z
beam
1st full betatron Oscillation period
xB
x
y
z
beam
2nd full betatron Oscillation period E.C.
Aschenauer 25Varenna, July 2011
spin depolarizing resonancespin depolarizing resonance
Imperfection resonance Source: dipole
errors, quadrupole mis-alignments
Resonance location:
G = k k is an integer
Intrinsic resonance Source: horizontal
focusing field from betatron oscillation
Resonance location:
G = kP±QyP is the periodicity of the
accelerator, Qy is the vertical betatron
tune
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Intr
insi
c sp
in r
eso
nan
ceQ
x=
28
.73
, Q
y=
29
.72
, em
it=
10
Spin depolarization resonance in RHICSpin depolarization resonance in RHIC
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For protons, imperfection spin resonances are spaced by 523 MeV
the higher energy, the stronger the depolarizing resonance
First invented by Derbenev and Kondratenko from Novosibirsk in 1970s
A group of dipole magnets with alternating horizontal and vertical dipole fields
rotates spin vector by 180o
Innovative polarized proton Innovative polarized proton acceleration techniques: Siberian acceleration techniques: Siberian
snakesnake
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Particle trajectory in a snake: Particle trajectory in a snake:
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Use one or a group of snakes to make the spin tune to be 1/2
How to preserve polarization using How to preserve polarization using Siberian snake(s)Siberian snake(s)
xB
y
z
beam
xB
y
z
beam
Break the coherent build-up of the perturbations on the spin vector
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PHENIX (p)
AGSAlternating Gradient Synchrotron
LINACBOOSTER
Pol. H- Source
Solenoid Partial Siberian Snake
200 MeV Polarimeter
Helical Partial Siberian Snake
Spin Rotators(longitudinal polarization)
Siberian Snakes
Spin Rotators(longitudinal polarization)
Strong AGS Snake
RHIC pC PolarimetersAbsolute Polarimeter (H jet)
STAR (p)
AGS Polarimeters
Spin flipper
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ANDY(p)
Polarized proton acceleration setup in Polarized proton acceleration setup in RHICRHIC
Energy: 23.8 GeV ~ 250 GeV (maximum store energy) A total of 146 imperfection resonances and
about 10 strong intrinsic resonances from injection to 100 GeV.Two full Siberian snakes
2
1 Qs
21s φφπ
1Q
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What is beam polarization? What is beam polarization?
Simple example: spin-1/2 particles (proton, electron)Can have only two spin states relative to certain axis Z: Sz=+1/2 and Sz =-1/2
2/12/1
2/12/1
ZZ
ZZ
SS
SS
NN
NNP
022
22
P
5.013
13
P
104
04
P
|P|<1
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How to measure proton beam How to measure proton beam polarizationpolarization
There are several established physics processes sensitive to the spin direction of the transversely polarized protons
Scattering to the right
Scattering to the left
AN – the Analyzing Power (|AN|<1)(left-right asymmetry for 100% polarized protons)
NAP
Once AN is known:
=N
lef t−N
right
Nlef t
+ Nright
=ANP
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Polarization MeasurementsPolarization Measurements
RightLeft
RightLeft
NN NN
NN
AAP
1
AN depends on the process and kinematic range of the measurements
pC elastic scattering
NAP
N
11)( Precision of
the measurements
N=NLeft+NRight
For (P)=0.01 and AN~0.01 N~108 !Requirements:
Large AN or/and high rate (N)Good control of kinematic range
-t=2MCEkin
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RHIC and Polarimetry RHIC and Polarimetry
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STAR (p)PHENIX (p)
AGS
LINAC BOOSTER
Pol. Proton Source500 A, 400 s
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)
RHIC PolarimetryRHIC Polarimetry
Polarized hydrogen Jet Polarimeter (HJet)Source of absolute polarization (normalization to other polarimeters)Slow (low rates needs lo-o-ong time to get precise measurements)
Proton-Carbon Polarimeter (pC)Very fast main polarization monitoring toolMeasures polarization profile (polarization is higher in beam center)Needs to be normalized to HJet
Local Polarimeters (in PHENIX and STAR experiments)Defines spin direction in experimental areaNeeds to be normalized to HJet
All of these systems are necessary for the proton beam polarization measurements and
monitoringE.C. Aschenauer 39Varenna, July 2011
Beam and target are both protons
Polarized H-Jet Polarimeter Polarized H-Jet Polarimeter
40
beam
beam
target
target
PPtAN
target
target beam
beam PP
RHIC proton beam
Forward scatteredproton
H-jet target
recoil proton 02 inout ppt
Ptarget is provided by Breit Rabi Polarimeter
Left-right asymmetry in elastic scattering due to spin-orbit interaction: interaction between (electric or strong) field of one proton and magnetic moment associated with the spin of the other proton
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H-jet system H-jet system
RHIC proton beam
Recoil proton
Height: 3.5 m
Weight: 3000 kg
Entire system moves along x-axis 10 ~ +10 mm to adjust collision point with RHIC beam.
IP12zy
x
target
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RF transitions (WFT or SFT)
|1> |2> |3> |4>
Separating Magnet (Sextuples)
H2 desociater
Holding magnet
2nd RF-transitions for calibration
P+ OR P
H = p+ + e
Atomic Beam Source
Scattering chamber
Breit-Rabi Polarimeter
Separating magnet
Ion gauge
|1> |3> |2> |4>
|1> |2>
|1> |2>
Ion gauge
Hyperfine structure
HHJetJet target system target system
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HJet: Identification of Elastic EventsHJet: Identification of Elastic Events
43
proton beam
Forward scatteredproton
proton target recoil proton
BLUE mode
YELLOW mode
Energy vs Channel #
ToF vs Energy
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Array of Si detectors measures TR & ToF of recoil proton. Channel # corresponds to recoil angle R.Correlations (TR & ToF ) and (TR & R ) the elastic process
HJet: PHJet: Ptargettarget
1 day
Breit-Rabi Polarimeter:
Separation of particles with different spin states in the inhomogeneous magnetic field (ala Stern-Gerlach experiment)
Nuclear polarization
Very stable for entire run period !Polarization cycle
(+/ 0/ ) = (500/50/500) s
Source of normalization for polarization measurements at RHIC
Nuclear polarization of the atoms:
95.8% 0.1%
After background correction:
Ptarget = 92.4% 1.8%
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HJet:HJet:
Provides statistical precision (P)/P ~ 0.10 in a store (6-8 hours)
target
target beam
beam PP Example from Run-2006
εbeam
εtarget
t=-2MpEkin
Use the same statistics (with exactly the same experimental cuts) to measure beam and target
(selecting proper spin states either for beam or for target)
Many systematic effects cancel out in the ratio
Ekin (MeV)Ekin (MeV)
target
beam
HJet Provides very clean and stable polarization measurements but with limited stat. precision
Need faster polarimeter! E.C. Aschenauer 45Varenna, July 2011
P-Carbon Polarimeter: P-Carbon Polarimeter:
Ultra thin Carbon ribbon Target(5 g/cm2)
11
3344
55
66
22
Si strip detectorsSi strip detectors(TOF, E(TOF, ECC))
18cm18cm
Polarized proton
Recoil carbon
Carbon target
LL NN or
RR NN or
or
Left-right asymmetry in elastic scattering due to spin-orbit interaction: interaction between (electric or strong) field of Carbon and magnetic moment associated with the spin of the proton
Pbeam N
ANpC
N NL NR
NL NR
Target Scan mode (20-30 sec per measurement)
Stat. precision 2-3%
Polarization profile, both vertical and horizontal
Normalized to H-Jet measurements over many fills (with precision <3%)
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pC: ApC: ANN
zero hadronic spin-flip
With hadronic spin-flip (E950)
Phys.Rev.Lett.,89,052302(2002)
pC Analyzing Power
Ebeam = 21.7GeVEbeam = 21.7GeV Ebeam = 100 GeVEbeam = 100 GeV
unpublishedRun04
hadflip
emflipnon
hadflipnon
emflipN CCA *
2
*
1
Elastic scattering: interference between electromagnetic and hadronic amplitudes in the Coulomb-Nuclear Interference
(CNI) region
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Polarization ProfilePolarization Profile
H-Jetp
~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
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Pol. Profile and Average PolarizationPol. Profile and Average Polarization
Carbon
Scan C target across the beamIn both X and Y directions
Target Position
Intensity
Polarizati
on
I
P
2
2
P
IR
YX
YX
YX
HJet
Exp RR
RR
RR
P
P
4
11
21
121
1
11
Run-2009:Ebeam=100 GeV: R~0.1 5% correction
Ebeam=250 GeV: R~0.35 15% correction
Ideal case: flat pol. profile (P= R=0)
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pC+HJet: Polarization vs FillpC+HJet: Polarization vs Fill
Run-2009 results (Ebeam=100 GeV)
Normalized to HJetCorrected for polarization profile (by pC)
P/P < 5%
Dominant sources of syst. uncertainties:
~3% - HJet background
~3% - pC stability (rate dependencies, gain drift)
~2% - Pol. profile“Yellow” beam
“Blue” beam
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Need for Local PolarimetersNeed for Local Polarimeters
E.C. Aschenauer 51Varenna, July 2011
ANDY(p)
STAR (p)PHENIX (p)
AGS
LINAC BOOSTER
Pol. Proton Source500 A, 400 s
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
Spin Rotators around experiments may change spin direction in experimental areas
Need to monitor spin direction in experimental areas
Local Polarimeter: PHENIXLocal Polarimeter: PHENIX
Utilizes spin dependence of very forward neutron production discovered in RHIC Run-2002 (PLB650, 325)
neutronchargedparticles
Zero Degree Calorimeter
Quite unexpected asymmetryTheory can not yet explain itBut already can be used for polarimetry! PAN
E.C. Aschenauer 52Varenna, July 2011
Monitor spin directionMonitor spin direction
Vertical ~ ±/2Radial ~ 0Longitudinal no asymmetry
Measures transverse polarization PT , Separately PX and PY
Longitudinal component:P – from CNI polarimeters
22TL PPP
Vertical
Radial
Longitudinal
-/2 0 /2
Asymmetry vs
E.C. Aschenauer 53Varenna, July 2011
STAR Local PolarimeterSTAR Local Polarimeter
3.3<||< 5.0 (small tiles only)
Utilizes spin dependence of hadron production at high xF:
Bunch-by-bunch (relative) polarization
E.C. Aschenauer 54Varenna, July 2011
Monitors spin direction in STAR collision regionCapable to precisely monitor polarization vs time in a
fill, and bunch-by-bunch
Now we have the polarised proton Now we have the polarised proton beam beam and and
know what the polarisation is,know what the polarisation is,what is nextwhat is next
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How do we measure thingsHow do we measure things DetectorsDetectors
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Design parameters for RHIC ppDesign parameters for RHIC pp
Parameter Unit p-p
relativistic , injection … 25.9
relativistic , store … 266.5
no of bunches, nb … 112
ions per bunch, Nb 1011 2.0
emittance eN x,y 95% mm-mrad 20
average luminosity 1030 cm-2s-1 150
polarization,store % 70
E.C. Aschenauer 57Varenna, July 2011
Stern-Gerlach ExperimentStern-Gerlach Experiment
Separation of spin states in the inhomogeneous magnetic field
E.C. Aschenauer 58Varenna, July 2011
SummarySummary Polarimetry is a crucial tool in RHIC Spin Program
Provides precise RHIC beam polarization measurements and monitoring
Provides crucial information for RHIC pol. beam setup, tune and development
RHIC Polarimetry consists of several independent subsystems, each of them playing their own crucial role (and based on different physics processes)
HJet: Absolute polarization measurements
pC: Polarization monitoring vs bunch and vs time in a fillPolarization profile
PHENIX and STAR Local Polarimeters: Monitor spin direction (through trans. spin component) at collision
E.C. Aschenauer 59Varenna, July 2011