Transcript E.C. Aschenauer EIC INT Program, Seattle 2010 - Week 8 Kinematics of elastic diffraction no cuts: 4x100 4x50 4x250 cuts: Q2 > 0.1 GeV && y.

E.C. Aschenauer
EIC INT Program, Seattle 2010 - Week 8
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Kinematics of elastic diffraction
no cuts:
4x100
4x50
4x250
cuts: Q2 > 0.1 GeV && y < 0.9 GeV
decay products of r & J/ψ
go more and more
forward with
increasing
asymmetry in
beam energies
E.C. Aschenauer
EIC INT Program, Seattle 2010 - Week 8
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Diffractive Physics: p’ kinematics
t=(p4-p2)2 = 2[(mpin.mpout)-(EinEout - pzinpzout)]
t=(p3–p1)2 = mρ2-Q2 - 2(Eγ*Eρ-pxγ*pxρ-pyγ*pyρ-pzγ*pzρ)
4 x 50
Diffraction:
?
p’
4 x 250
need “roman pots”
to detect the protons
and a ZDC for
neutrons
4 x 100
E.C. Aschenauer
EIC INT Program, Seattle 2010 - Week 8
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How to detect exclusive protons
 Detector concepts
 Roman Pots for protons / charged particles
 Zero Degree Calorimeters (ZDC) for neutrons
 Preshower & ECal for photons, important for eA  e’A’g
 Challenges
 angular emittance of the beam
eRHIC: 0.1 mrad
 how close to the beam can the roman pots go
normally 10s  1mrad
 geometric acceptance of magnets
 need thin exit windows for particles
 need most likely more than one place to put roman pots
E.C. Aschenauer
EIC INT Program, Seattle 2010 - Week 8
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eRHIC Detector Concept
Forward / Backward
Spectrometers:
2m
4m
 central detector acceptance: very high coverage -5 < h < 5




 Tracker and ECal coverage the same
 crossing angle: 10 mrad; Dy = 2cm and Dx = 2/4cm (electron/proton direction)
Dipoles needed to have good forward momentum resolution and acceptance
DIRC, RICH hadron identification  p, K, p
low radiation length extremely critical  low lepton energies
precise vertexE.C.
reconstruction
(< 10 EIC
mm)INT
 Program,
separate
Beauty
Charmed
Meson 5
Seattle
2010 and
- Week
8
Aschenauer
IR-Design-Version-I
eRHIC - Geometry high-lumi IR with β*=5 cm, l*=4.5 m
and 10 mrad crossing angle
10
20
0.329 m
0.188036 m
0.44 m
Assume 50% operations efficiency
 4fb-1 / week
30 GeV e-
30
60 m
90 m
© D.Trbojevic
E.C. Aschenauer
EIC INT Program, Seattle 2010 - Week 8
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A detector integrated into IR – Version 1
space for
e-polarimetry
and luminosity
measurements
ZDC
FPD
FED
 for ERL solution need not to measure electron polarization bunch by bunch
 need still to integrate luminosity monitor
 need still to integrate hadronic polarimeters, maybe at different IP
E.C. Aschenauer
EIC INT Program, Seattle 2010 - Week 8
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Can we detect DVCS-protons and Au break up p
 track the protons through solenoid, quads and dipole with hector
 beam angular spread 0.1mrad at IR
 Quads +/- 5mrad acceptance; geometric acceptance: 1.5cm
 Proton-beam: p’z> 0.9pz
 100 GeV: ptmax < 0.45 GeV
 suboptimal as we loose intermediate pt (0.4 – 1.2 GeV)/ t range
 solution could be to do the same as for the electrons swap the
dipole and quads  lumi goes down  see next slides
proton track Dp=10%
E.C. Aschenauer
proton track Dp=20%
EIC INT Program,
proton track Dp=40%
Equivalent to fragmenting
protons from Au in Au optics
Seattle(197/79:1
2010 - Week~2.5:1)
8
8
IP configuration for eRHIC – Version-II
pc/2.5
Estimated b*≈ 8 cm
4.5 cm
neutrons
11.2 cm
q=10 mrad
e IP
2
4
6
8
Dipole:
2.5 m, 6 T
q=18 mrad
E.C. Aschenauer
10
12
14
16
Quad Gradient:
200 T/m
EIC INT Program, Seattle 2010 - Week 8
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IP configuration for eRHIC – Version-II
5.75 cm
10
17.65 m
20
0.44843 m
0.39065 m
0.333 m
D5
30
60.0559 m
90.08703 m
E.C. Aschenauer
EIC INT Program, Seattle 2010 - Week 8
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Can we detect “exclusive” protons
 lets see acceptance now
 beam angular spread 0.1mrad at IR
 Dipole +/- 10 mrad; geometric acceptance: +/- 11.5 cm
 Quads +/- 3 mrad acceptance; geometric acceptance: < 1.5cm
 Proton-beam: p’z> 0.9pz  lets assume pz = pbeam
 maximal pt
 100 GeV: ptmax < 1 GeV
 50 GeV: ptmax < 0.8 GeV
 minimal pt  assume 10s distance of roman pot to beam
 100 GeV: ptmin ~ 100 MeV
 50 GeV: ptmin ~ 50 MeV
E.C. Aschenauer
EIC INT Program, Seattle 2010 - Week 8
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How to measure coherent diffraction in e+A ?
 Beam angular divergence limits smallest
outgoing Qmin for p/A that can be
measured
 Can measure the nucleus if it is separated
from the beam in Si (Roman Pot)
“beamline” detectors
 pTmin ~ pzAtanθmin
For beam energies = 100 GeV/n and
θmin = 0.1 mrad
 Large momentum kicks, much larger
than binding energy (~8 MeV)
 Therefore, for large A, coherently
diffractive nucleus cannot be separated
from beamline without breaking up
E.C. Aschenauer
species
(A)
d (2)
Si (28)
Cu (64)
In (115)
Au (197)
U (238)
EIC INT Program, Seattle 2010 - Week 8
pTmin
(GeV/c)
0.02
0.22
0.51
0.92
1.58
1.90
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How to measure coherent diffraction in e+A ?
 Rely on rapidity gap method
Purity Efficiency
 simulations look good
 high eff. high purity
possible with gap alone
~1% contamination
~80% efficiency
 depends critical on detector
hermeticity
 improve further by veto on
breakup of nuclei (DIS)
 Very critical
 mandatory to detect nuclear
fragments from breakup
E.C. Aschenauer
rapidity
EIC INT Program, Seattle 2010 - Week 8
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BACKUP
E.C. Aschenauer
EIC INT Program, Seattle 2010 - Week 8
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6.5 T magnet, 2.5 m long
4.5 cm
E.C. Aschenauer
EIC INT Program, Seattle 2010 - Week 8
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Quads for β*=5 cm
© B.Parker
E.C. Aschenauer
EIC INT Program, Seattle 2010 - Week 8
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