a detector for ( m)erhic

EIC-IAC @ JLab, November 2009 1

A Detector for (M)eRHIC

E.C. Aschenauer


Detector Requirements from Physics

E.C. Aschenauer

ep-physics the same detector needs to cover inclusive (ep -> e’X),

semi-inclusive (ep -> e’hadron(s)X) and exclusive (ep -> e’p ) p reactions

large acceptance absolutely crucial (both mid and forward-rapidity) particle identification is crucial

e, p, K, p, n over wide momentum range and scattering angle excellent secondary vertex resolution (charm)

particle detection to very low scattering angle around 1o in e and p/A direction

in contradiction to strong focusing quads close to IP

small systematic uncertainty for e/p polarization measurements

very small systematic uncertainty for luminosity measurement

eA-physics requirements very similar to ep

challenge to tag the struck nucleus in exclusive and diffractive reactions.


Event kinematics scattered lepton

E.C. Aschenauer

DIS

DIFFRACTIVE

4x50 4x250

175o

20x250

179o

withoutmagneticfield


Event kinematics produced hadrons (p+)

E.C. Aschenauer

DIS

DIFFRACTIVE

4x504x25020x250

withoutmagneticfield

DIS:smalltheta important

EIC-IAC @ JLab, November 2009 5E.C. Aschenauer

Include:recoil proton plots and update the other ones for better visibility

EIC-IAC @ JLab, November 2009E.C. Aschenauer

6

STAR

PH

EN

IX

2 x 200 m SRF linac4 (5) GeV per pass5 (4) passes

Polarized e-gun

Beamdump

4 to 5 vertically separatedrecirculating passes

Cohere

nt

e-c

oole

r

5 mm

5 mm

5 mm

5 mm

20 GeV e-beam

16 GeV e-beam

12 GeV e-beam

8 GeV e-beam

Com

mon

vacu

um

ch

am

ber

Gap 5 mm total0.3 T for 30 GeV

eRHICdetector

MeRH

IC

dete

ctor

10-20 GeV e x 325 GeV p 130 GeV/u Au

possibility of 30 GeV @low current operation

ERL-based eRHIC Design


A Detector for Diffraction

E.C. Aschenauer

e

p

HadronicCalorimeter

EM Calorimeter

Si tra

ckin

g

stat

ions

Compact – fits in dipole magnet with inner radius of 80 cm.Long - |z|5 m

Design by Allen Caldwell:

2x14 Si tracking stations


First ideas for a detector concept

E.C. Aschenauer

Dipol3Tm

Dipol3Tm

Solenoid (4T)

ZDC

FPD

FED// //

Dipoles needed to have good forward momentum resolution Solenoid no magnetic field @ r ~ 0

DIRC, RICH hadron identification p, K, p high-threshold Cerenkov fast trigger for scattered lepton radiation length very critical low lepton energies


IR-Design for MeRHIC I @ IP-2

E.C. Aschenauer

no synchrotron shielding included IP-2: height beam-pipe floor ~6’ (with digging

~10’)


Diffractive events

E.C. Aschenauer

include 1 or 2 slides from Matt on diffractive studies for eA to make thepoint where the nuclei go, like Thomas slide 19


Detection from hadron beam fragments

Tagging from Au fragments and p/n in ep suppress incoherent scattering / ensure exclusivity

neutrons are detected in ZDC protons use magnetic rigidity Au:p 2.5:1

DX magnets disturbs p tagging

E.C. Aschenauer


IR-Design for MeRHIC IP-2

E.C. Aschenauer

no synchrotron shielding included allows p and heavy ion decay product tagging IP-2: height beam-pipe floor ~6’ (with digging ~10’)


First ideas for a detector concept

E.C. Aschenauer

Dipol3Tm

Dipol3Tm

Solenoid (4T)

ZDC

FPD

FED// //

Dipoles needed to have good forward momentum resolution Solenoid no magnetic field @ r ~ 0

DIRC, RICH hadron identification p, K, p high-threshold Cerenkov fast trigger for scattered lepton radiation length very critical low lepton energies


Basis for Detector design

E.C. Aschenauer

explain the basis for the detector design, like dirc copy of Babar ….


Drift Chambers central trackingala BaBar

MeRHIC Detector in Geant-3

E.C. Aschenauer

no hadronic calorimeter in barrel, because of vertical space @ IP-2

Silicon Stripdetector



E.C. Aschenauer


Summary

Have done first steps on a detector design Optimizations needed

magnetic fieldsdo we need 4T for solenoid and 3Tm for dipole

what radiation length can we tolerate @ low e’ momentum

optimize distance Dipole to Solenoid impact of beam lines through the detector on physics

need to optimize acceptance at low scattering angleneed acceptance down to 1o

need to include lepton polarimeter in IR design need to include luminosity monitor into IR design

E.C. Aschenauer


Start immediately at 12o’clock

E.C. Aschenauer

Detector cost savingshave MeRHIC-detector @ IP-12

fully staged detector from MeRHIC to eRHIC vertical space much bigger need to buy magnets only once can stage detector components, i.e. hadronic calorimeter no moving of components

only advantages


12:00 experimental area

E.C. Aschenauer


Work done @ JLAB


ions

electrons

solenoid dipole bendingscattered protons “up”

IP withcrossing angle electron FFQs

ion FFQs

Distance from IP to electron FFQ: 6 m to ion FFQ: 9m

Electron FF quad

Distance from IP

length Field strength

Beam size sx

@ 3 GeV

Beam size sy

@ 3 GeV

Quad 1 6.0 meter 50 cm -1.14 kG/cm

5 mm 4 mm

Quad 2 6.75 meter

120 cm 0.71 kG/cm

8 mm 3 mm

Quad 3 8.7 meter 50 cm -0.75 kG/cm

4 mm 4 mm

Modest electron final focusing quad field requirements quads can be made small

ELIC Detector/IR Layout

E.C. Aschenauer


8 meters (for scale)

140 degrees

Tracking

TOF

dipole

solenoid

RICH

ECAL

DIRC

HCAL

HTCC

Offset IP?

Ion beame beam

dipole1st (small) electron FF quad @ 6 m

ELIC detector cartoon - Oct. 09

E.C. Aschenauer

Additional electron detection (tracking, calorimetry) for low-Q2 physics not on cartoon


Central 4T solenoid with 5 meter length and 4 meter ID Need to add good particle identification detectors up to 40 degrees on ion side drives large ID to keep this area “open” 4T field renders O(1%) or better momentum resolution for particles with momentum < 10 GeV (and angles > 40 degrees)

Optimize detector to detect particles down to (at least) one degrees Add 2-3 Tm dipole field to improve momentum resolution at forward angles. Two solutions: add dipole, or add dipole to solenoid? Can in principle also have split dipole, with different polarity before/after IP, if this helps accelerator design.

5T solenoid with 0.6T dipole winding:Integrated transverse (By) field strength

@ 90 degrees 10.9 Tm@ 40 degrees 15.3 Tm@ 1 degree 1.4 Tm

May present alternate solution if space is at a premium & 1.4 Tm sufficient field strength at 1o.

Note: all configurations iron free at moment

Dipole coils

ELIC Detector Magnetic Field

E.C. Aschenauer


kk'

ZP ZP'

q'

qMm

e + AZ e + AZ + (,,J/)Determining exclusivity requires tagging the nucleus in the final state. The typical scale of transverse momentum transfer is given by the rms nuclear radius.

(for nuclei from 4He to 20Ne, this scale ranges from 125 MeV/c to 75 MeV/c)

Recoil Tagging in Deeply Virtual Exclusive Reactions on Nuclei

E.C. Aschenauer

For Nuclei ≥ 4He, the recoil nucleus is – INSIDE the transverse admittance of the FF Quads

• Qms ≈ 1 mr PA,transverse ≈ Z·(60 MeV/c) (for 60 GeV ion beam)

• Beam spread is larger than 1/RA scale for nuclear imaging.

• Z·(60 MeV/c ) > (0.2 GeV/c)/A1/3 (≥75 MeV/c for AZ< 20Ne) – OUTSIDE the longitudinal admittance of the ring lattice!!!

The nuclei may be detectable at high resolution with far forward tracking in the lattice by having large dispersion ELIC study


Far Forward Ion Tagging at (60 GeV/c) Z

Sample optics at token Roman Pot Telescope position ELIC typical: Dispersion D = 1 m, Beta function b* = 2 m ELIC typical: (x,Q) = (250 mm, 125 mr) rms Use a 10sx Beam Stay Clear (BSC) distance 2.5 mm Ions are detectable for |dPA||/PA| > BSC/D = 2.5 x 10-3.

Skewness 2z (~x/A) of Deep Virtual reaction = long. momentum fraction of a nucleon in projectile ion.Skewness acceptance: 2z > (2.5x10-3)A 0.05 for 20Ne.

Assumption: 1 m drift with 100 mm spatial resolution dQ = 100 mr equal to beam Qrms. PA’ Momentum Resolution = sx/D = 2.5 x 10-4.

D|| = (k-k’-q’) || = (PA’-PA’)|| s(D||) = (4 x 10-4)(30 GeV/c) A = (12 MeV/c) A

Exclusivity constraint D2 = 2MA (PA’-PA) Using ELIC arc as spectrometer to a longitudinal

momentum transfer resolution of 10-4 by increasing dispersion @ IR will be explored in more detail

E.C. Aschenauer


BACKUP


Zeus @ HERA I

E.C. Aschenauer


Zeus @ HERA II

E.C. Aschenauer


Hera I vs Hera II

E.C. Aschenauer

Focusing Quads close to IPProblem for forward acceptance

a detector for ( m)erhic

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