e.c. aschenauer1. requirements from physics on ir e.c. aschenauer 2 summarized at: hadron beam:
TRANSCRIPT
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R&D Proposal for an electron polarimeter, a luminosity monitor and a low Q2-tagger
RD 2013-6
E.C. Aschenauer
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Requirements from Physics on IR
E.C. Aschenauer
Summarized at: https://wiki.bnl.gov/eic/index.php/IR_Design_Requirements
Hadron Beam:1. the detection of neutrons of nuclear break up in the outgoing
hadron beam direction location/acceptance of ZDC2. the detection of the scattered protons from exclusive and
diffractive reaction in the outgoing proton beam direction the detection of the spectator protons from 3He and Deuterium location/acceptance of RP; impact of crab-cavities on forward scattered protons
Lepton Beam:3. the beam element free region around the IR 4. minimize impact of detector magnetic field on lepton beam synchrotron radiation5. space for low Q2 scattered lepton detection6. space for the luminosity monitor in the outgoing lepton beam
direction7. space for lepton polarimetry
Important
EIC is a high luminosity machine 1033 cm-2s-1
such controlling systematics becomes crucial
luminosity measurement
lepton and hadron polarisation measurement
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eRHIC-Detector Design Concept
ToRoman Pots
Upstreamlow Q2
tagger
HCAL HCAL
ECAL PWO ECAL WScinECAL W-Scintillator
RICHRICH
PID:-1<h<1: DIRC or proximity focusing Aerogel-RICH1<|h|<3: RICH Lepton-ID: -3 <h< 3: e/p 1<|h|<3: in addition Hcal response & g suppression via tracking|h|>3: ECal+Hcal response & g suppression via tracking-5<h<5: Tracking (TPC+GEM+MAPS)
DIRC/proximity RICH
h-h
E.C. Aschenauer
ToLumi
detector
e-Polarimeter where to put
before or after IR
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Example: Longitudinal Spin Structure
E.C. Aschenauer
Can DS and DG explain it all ?
Contribution to proton spin to date:Gluon: 20% (RHIC) Quarks: 30% (DIS)MISS 50% low x
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g1p the way to find the Spin
E.C. Aschenauer
5 x 250 starts here
5 x 100 starts here
hep-ph:1206.6014 (M.Stratmann, R. Sassot, ECA)cross section:
pQCD scaling violations
world data noweRHIC 5x100/250 GeV
dramatic reduction of uncertainties:
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• can expect ~5-10% uncertainties on ΔΣ and Δg
BUT need to control systematics
current data
w/ eRHIC data
Can we solve the spin sum rule ?
E.C. Aschenauer
total quark spin DS
gluonspin Dg
✔
✔
orbital angular momentum
can beextracted throughexclusive reactions
for details seeD. Mueller, K. KumerickiS. Fazio, and ECAarXiv:1304.0077
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Impact on ∫Dg from systematic uncertainties
E.C. Aschenauer
Need systematics ≤ 2%
arXiv: 1206.6014
Dominant systematics:
Luminosity Measurement Relative Luminosity
needs to be controlled better then ALL
~10-4 at low x
Absolut polarization measurements:electron Pe and hadron Pp
relativeluminosity
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Luminosity Measurement: physics processes
E.C. Aschenauer
Goals for Luminosity Measurement:
Integrated luminosity with precision δL< 1%
Measurement of relative luminosity: physics-
asymmetry/10
Fast beam monitoring for optimization of ep-
collisions and control of mid-term variations of
instantaneous luminosity
requires ‘alternative’ methods for luminosity
determination
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Polarization and Luminosity Coupling Concept: Use Bremsstrahlung ep epg as reference cross section
normally only single photon counting Hera: reached 1-2% systematic uncertainty
eRHIC BUTs: with 1033cm-2s-1 one gets on average of 23 bremsstrahlungs
photons/bunch for proton beam A-beam Z2-dependence this will challenge single photon measurement under 0o
coupling between polarization measurement uncertainty and uncertainty achievable for lumi-measurement
no experience no polarized ep collider jet have started to calculate a with the help of Vladimir Makarenk
(NC PHEP BSU, Minsk), did these calculations for ZEUS and is now at CERN to work on CLIC-QED calculations
hopefully a is smallE.C.
Aschenauer
Important
need to monitor not only polarisation level but also
polarisation bunch current correlation
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Luminosity Measurement Concept: Use Bremsstrahlung ep epg as reference cross section
normally only g is measured Hera: reached 1-2% systematic uncertainty
E.C. Aschenauer
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Luminosity Detectors zero degree calorimeter
high rate measured energy proportional to # photons subject to synchrotron radiation
alternative pair spectrometer
Vacuum
Chamber
L3
ge+/e-
g e-
e+
Dipole Magnetvery thinConverter
L2L1
Segmented ECal
The calorimeters are outside of the primary synchrotron radiation fan The exit window conversion fraction reduces the overall rate The spectrometer geometry imposes a low energy cutoff in the photon spectrum, which depends on the magnitude of the dipole field and the transverse location of the calorimeters
12E.C. Aschenauer
Detector and IR-DesignAll optimized for dedicated detectorHave +/-4.5m for main-detector p: roman pots / ZDC e: low Q2-tagger
e
eRHIC-Detector:collider detector with-4<h<4 rapidity coverageand excellent PID
p
eRHICDetector
100$-question:Can we combine low Q2-taggerlumi-monitorand compton polarimeterin one detector system?
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eRHIC Lepton Beam How to generate 50 mA of polarized electron beam? Polarized cathodes are notorious for dying fast even at mA beam currents
eRHIC design is using the idea of a “Gatling” electron gun with a combiner? 20 cathodes one proton bunch collides always with electrons from one specific cathode
Important questions: What is the expected fluctuation in polarisation from cathode to cathode in the
gatling gun from Jlab experience 3-5%
What fluctuation in bunch current for the electron do we expect limited by Surface Charge, need to see what we obtain from prototype gun
Do we expect that the collision deteriorates the electron polarisation. A problem discussed for ILC influences where we want to measure polarisation in the ring
How much polarisation loss do we expect from the source to flat top in the ERL.
Losses in the arcs have been significant at SLC
Is there the possibility for a polarisation profile for the lepton bunches if then in the longitudinal direction can be circumvented with 352 MHz RF
Challenge:
Integrate Compton polarimeter into IR and Detector
design
together with Luminosity monitor and low Q2-tagger
longitudinal polarisation Energy asymmetry
segmented Calorimeter to measure possible
transverse polarisation component position
asymmetry
E.C. Aschenauer
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Lepton Polarization
E.C. Aschenauer
Method: Compton backscattering
572 nm pulsed laser laser transport system: ~80m laser light polarisation measured
continuously in box #2
Multi-Photon Mode:Advantages: - eff. independent of brems. bkg and photon energy cutoff - dP/P = 0.01 in 1 min
Disadvantage: - no easy monitoring of calorimeter performance
Am = (I3/2 – I1/2) / (I3/2 + I1/2) = Pe Pl Ap; Ap=0.184
Result:
Have achieved 1.4% uncertainty at
HERA
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ep
PolarimeterLaser
laser polarisationneeds to be monitored Measure Polarisation at IP
overlap of bremsstrahlungs and compton photons only possible if we have number of empty p-bunches = # cathods
luminosity loss Measure after / before IP need to measure at location spin is fully longitudinal or transverse
1/6 turn should rotate spin by integer number of π After IP:
does collision reduce polarisation? need to measure at location, where bremsstrahlung contribution is small
Before IP: need to find room for photon calorimeter
The lepton polarimeter: Location?
Summary:
all of this needs to be carefully modeled
work to integrate eRHIC IR into EICroot has started
Comptonphoton
detector
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Low Q2-taggere’-tagger:
detect low Q2 scattered electrons quasi-real photoproduction physics
possibly also detect lepton from lepton polarimeter compton scattering
design could follow the Hall-D tagger designpileup can be avoided by fine segmentation of tagger detectors
E.C. Aschenauer
e’-detector
Ee
Array of Scintillatorsvery finely spaced
might need less segmentationScintillator Calorimeter
Electron Tagger as Hall-D
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Microscope
Hodoscope support frame
Tagger strong-back
Vacuum Chamber supports
Magnet steel Vacuum chamber
Coils
Electron beam
Photon
beam
post-bre
msstra
hlungs
electrons
Hodoscope
E.C. Aschenauer
tagged scattered electrons from Bremsstrahlung from ~1 GeV to 6 GeV photon energy 6 GeV to 12 GeV
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Deliverables Luminosity:
determine a in s0(1+aPePp) through calculation develop a MC for (un)polarised bremsstrahlung in ep/eA
collisions integrate luminosity detectors into the IR-design develop detector performance requirements follow up
with detector R&D for calorimeter technology, i.e. Diamond
Polarimetry: determine performance requirements for fast and
“slow” polarisation measurement integrate polarimeter into IR-design and as close as
possible to IP simulation package of polarimeter
Low Q2-tagger: determine the detector performance requirements
can scattered leptons from bremsstrahlung be separated from low-Q2 DIS segmentation of tagger-detectors
Integrate into IR-designE.C.
Aschenauer
Goal to increase collaboration:
Will seek collaboration with Luminosity and low-Q2
tagger group from LHeC
Request:
1 postdoc position for 2 years starting in FY14
travel funding for the group 10k$ / year
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What needs to be covered BY THE DETECTORe’
t
(Q2)e
gL*
x+ξ x-ξ
H, H, E, E (x,ξ,t)
~~
, ,g p J/Y
p p’
Inclusive Reactions in ep/eA: Physics: Structure Fcts.: g1, F2, FL
Very good electron id find scattered lepton Momentum/energy and angular resolution of e’ critical scattered lepton kinematics
Semi-inclusive Reactions in ep/eA: Physics: TMDs, Helicity PDFs flavor separation, dihadron-corr.,… Kaon asymmetries, cross sections Excellent particle ID: p±,K±,p± separation over a wide range in h full F-coverage around g* Excellent vertex resolution Charm, Bottom identification
Exclusive Reactions in ep/eA: Physics: GPDs, proton/nucleus imaging, DVCS, excl. VM/PS prod. Exclusivity large rapidity coverage rapidity gap events ↘ reconstruction of all particles in event high resolution in t Roman potsE.C.
Aschenauer
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RHIC Hadron PolarisationAccount for beam polarization decay through fill P(t)=P0exp(-t/tp) growth of beam polarization profile R through fill
pCarbon polarimeter
x=x0
ColliderExperiments
),(),( 01011 yxIyxPP
),(),(),( 2111 yxIyxIyxPP
correlation of dP/dt to dR/dt
for all 2012 fillsat 250 GeV
Polarization lifetime has consequences for physics analysis different physics triggers mix over
fill different <P>
Result:
Have achieved 6.5% uncertainty for DSA and 3.4 for
SSAwill be very challenging to reduce to 1-2%
E.C. Aschenauer
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RHIC: Polarisation-Bunch Current Correlation
E.C. Aschenauer
0 50 100 150 200 250 300
-0.07-0.06-0.05-0.04-0.03-0.02-0.01
00.010.020.03
Correlator vs. Energy Up Spin
B1B2Y1Y2
Energy [GeV]
Corr
elat
or
0 50 100 150 200 250 300
-0.08
-0.06
-0.04
-0.02
0
0.02
0.04
Correlator vs. Energy Down Spin
B1B2Y1Y2
Energy [GeV]
Corr
elat
or
Data from 2012-Run:
Small anti-correlationbetween polarisation andbunch current at injectionwhich washes out at collision energies
Improvements of hadron polarisation measurements:
continuously monitor molecular fraction in the H-Jet
find longer lifetime and more homogenious target
material for the pC polarimeters
can we calibrate energy scale of pC closer to Ekin(C) in
CNI
alternative detector technology for Si-detectors to
detect C
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eRHIC: high-luminosity IR
10 mrad crossing angle and crab-crossing High gradient (200 T/m) large aperture Nb3Sn focusing magnets Arranged free-field electron pass through the hadron triplet magnets Integration with the detector: efficient separation and registration of
low angle collision products Gentle bending of the electrons to avoid SR impact in the detector
Proton beam lattice
© D.Trbojevic, B.Parker, S. Tepikian, J. Beebe-Wang
e
p
Nb3Sn
200 T/m
G.Ambrosio et al., IPAC’10
eRHIC - Geometry high-lumi IR with β*=5 cm, l*=4.5 mand 10 mrad crossing angle 1034 cm-2 s-1
20x250
20x250
GeneratedQuad aperture limitedRP (at 20m) accepted
E.C. Aschenauer
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Integration into Machine: IR-Design
E.C. Aschenauer
space for low-Q e-tagger
Outgoing electron direction currently under detailed design detect low Q2 scattered leptons want to use the vertical bend to separate very low-Q e’ from beam-electrons can make bend faster for outgoing beam faster separation for 0.1o<Q<1o will add calorimetry after the main detector
Exclusive Reactions: Event Selection
E.C. Aschenauer
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leading protons are never in the main detector
acceptance at EIC (stage 1 and 2)
eRHIC detector acceptance
e’(Q2)
e gL*
x+ξ x-ξ
H, H, E, E (x,ξ,t)~~
g
p p’t
proton/neutron tag method
o Measurement of t o Free of p-diss backgroundo Higher MX rangeo to have high acceptance
for Roman Pots / ZDC challenging IR design
Diffractive peak
x L=p' zp z
≈1− x IP
Need for roman pot
spectrometerANDZDC
5x100 GeV 5x100 GeV20x250 GeV
t-Measurement using RP
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Accepted in“Roman Pot” at 20m
Quadrupoles
acceptance
10s from the beam-
pipe
• high‐|t| acceptance mainly limited by magnet aperture
• low‐|t| acceptance limited by beam envelop (~10σ)
• |t|‐resolution limited by– beam angular divergence ~100μrad for small |t|– uncertainties in vertex (x,y,z) and transport– ~<5-10% resolution in t (follow RP at STAR)
Simulation based on eRHIC-IR
GeneratedQuad aperture limitedRP (at 20m) accepted
20x250
E.C. Aschenauer
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Spectator proton tagging for He-3
E.C. Aschenauer
Momentum smearing mainly due to Fermi motion + Lorentz boost Angle <~3mrad (>99.9%)
after IR magnets at 20m
at 20m after IR magnets RP acceptance +10s beam clearance 90% tagging efficency
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Kinematics of Breakup Neutrons
Results from GEMINI++ for 50 GeV Au
+/-5mrad acceptance totally sufficient
Results:With an aperture of ±5 mrad we are in good shape• enough “detection” power for t > 0.025 GeV2
• below t ~ 0.02 GeV2 photon detection in very forward direction all accounted in IR designQuestion:• For some physics needed rejection power for
incoherent: ~104
Critical: ZDC efficiency
E.C. Aschenauer
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ep
PolarimeterLaser
laser polarisationneeds to be monitored
Allows to measure polarisation right at IR, but only for non-colliding bunches need as many non-colliding bunches as cathods no bremsstrahlungs background
ECal: needs to be radiation hard (sees synchrotron radiation fan) possible technology diamante calorimeter ILC FCal will be used to detect compton photons
e’-tagger: detect low Q2 scattered electrons quasi-real photoproduction physics detect lepton from compton scattering
pair spectrometer: only possible high precision luminosity measurement
~ECAL
small θe’-tagger
pairspectrometer
A possible layout for all in one
Summary:
all of this needs to be carefully modeled
work to integrate eRHIC IR into EICroot has started