overview oferhic detector design studies

Bernd SurrowBernd Surrow

Bernd SurroweA eRHIC meeting BNL, October 20, 2006

Recirculating linac injector

5-10 GeV static electron ring

e

EBIS

RHIC

AGS

BOOSTER

RHIC

LINAC

Polarized proton source

e-cooling

Overview ofeRHIC detector Overview ofeRHIC detector design studiesdesign studies

Overview ofeRHIC detector Overview ofeRHIC detector design studiesdesign studies


OutlineOutline

DIS - Kinematics and

Structure Functions

QCD basics

Structure Function

Measurement

Kinematics

reconstruction

eRHIC - Detector

requirements

eRHIC - Detector

design aspects

Concluding remarks


Measure of resolution power

Measure of momentum fraction of struck quark

Measure of inelasticity

Quantitative description of electron-proton scattering

DIS - DIS - Kinematics and Structure Functions and Structure FunctionsDIS - DIS - Kinematics and Structure Functions and Structure Functions


Rutherford cross-section

DIS - Kinematics and Structure FunctionsDIS - Kinematics and Structure FunctionsDIS - Kinematics and Structure FunctionsDIS - Kinematics and Structure Functions


constantPoint-like

Homogeneous sphere with edge oscillating

Exponential-like constantdipole

Scattering of electron (Spin 1/2) on point-

charge charge (Spin 0): Mott cross-section

Take into account finite charge

distribution: Form factor

12C

Hofstadter, 1953

Quantify the nucleus structure: Form factors (Elastic scattering)



Rosenbluth separation method:

Electron scattering on hydrogen target: 188MeV

Mott

Dirac

Experiment

Point-charge, point-moment

θ

dσ/

dΩ

[cm

2 /sr

]Hofstadter

Scattering of electron (Spin 1/2) on proton (Spin 1/2)

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Nobel Prize 1961



Quantify the nucleon structure: Form factors (Elastic scattering)



Friedman, Kendall and Taylor

Scattering on point-like objects: Quarks!

Scattering of electron (Spin 1/2) on proton (Spin 1/2)




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Nobel Prize 1990 QuickTime™ and a

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Here: Deep-inelastic scattering (DIS)

Quantify proton structure: Structure functions (Inelastic case)



Longitudinal structure function: FL

Structure function measurement: Formalism

In terms of laboratory variables:

Formulate this now in relativistic invariant quantities:

Instead of W1 and W2, use: F1 and F2:



EvolutionEvolution:

Beyond Quark-Parton model, Parton densities become functions of Q2

Predict Q2 dependence of parton distribution functions (evolution equations)

Asymptotic freedomAsymptotic freedom:

αs → 0 at short distances:⇒ perturbative QCD

αs large at long distances: ⇒ non-perturbative QCD

non-perturbative part

FactorizationFactorization: hard scale Q2

Fundamental QCD ingredients

QCD basicsQCD basicsQCD basicsQCD basics


Discovery of asymptotic freedom in the theory of strong interaction (Quantum Chromo Dynamics): Nobel prize in physics 2004

Leading-log approximation:

Asymptotic freedom



Three steps:

Partons (quarks/gluons) in initial state: Long distance (non-perturbative QCD domain)

⇒ Parton (quarks/gluons) distribution functions

Hard interaction: Small distances (high energies) (perturbative QCD domain)

⇒ Cross-section prediction

Quarks in final state: Long distance (non-perturbative QCD domain):

⇒ Quarks fragment into observable hadrons described by fragmentation functions

Unpolarized proton structure:

long-range short-range long-range

f1

f2

Factorization



Parton model Gluon radiation

Splitting function

Logarithmic violation of scaling

Quark densities depend on x and Q2:

Evolution (1)

The presence of QCD related diagrams leads to a modification of F2



Singlet distribution

Gluon distributionProbability of finding a parton of type i with

momentum fraction x which originated from

parton j having momentum fraction y!

DGLAP evolution equations: G. Altarelli and G. Parisi, Nucl. Phys. B 126 (1977) 298; V. Gribov and L.N. Lipatov, Soc. J. Nucl. Phys. 15 (1972) 438; L.N. Lipatov, Soc. J. Nucl. Phys. 20 (1975) 96; Y.L. Dokshitzer, Soc. Phys. JETP 46 (1977) 641.

Evolution (2)Consider the change of the quark density Δq(x,Q2) over an interval of ΔlogQ2

General including other types of splitting functions:



2. Determination of cross-section and extraction of F2:

Efficiency Luminosity

Number of selected

events Background

bin inx and Q2

1. Determination of kinematics (e.g. electron method):

Structure function measurement: Kinematic coverage and measurement

Structure Function MeasurementStructure Function MeasurementStructure Function MeasurementStructure Function Measurement


F2

F2

Three valence

quarks

Three bound valence

quarks

F2

Valence quarks and QCD sea

Three valence quarks and sea quarks +

gluons QCD

x: Momentum fraction of struck quark

Proton = valence quarks + QCD sea

Structure function measurement: Picture of the Proton



Large Q (short λ)

At higher and higherresolutions, the quarksemit gluons, which also emit gluons, which emit quarks, which…!

Low Q (large wavelength λ)

Medium Q (medium λ)

• Evolution



Strong violation of scaling at low x and high Q2

In contrast to:

Low Q2 high x!

scaling

Violation of scaling: QCD prediction

Structure function measurement: Q2 and x dependence



Extracting parton distribution functions

Determine F2QCD in terms of parton distribution functions

Evolve F2QCD through parton distribution functions based on evolution equations

Minimize χ2 in terms of F2QCD and F2

data by adjusting parameters in xfi(x,Q2)

Net result: QCD prediction for xfi(x,Q2) and therefore F2(x,Q2)

Various global pdf analyses:GRV

CTEQ

MRST

ZEUS/H1


Low x: λi High x: ηi

i: valence (u,d), sea (s) and gluon (g)


FL negative at low Q2 and low x!

Extrapolation of ZEUS NLO DGLAP fit towards low Q2



Structure Function MeasurementStructure Function Measurement

Reconstruction of F2


Structure Function MeasurementStructure Function Measurement

Reconstruction of F2

Correct for FL to get F2!Requires unfolding!


Electron method: scattered electron

Jacquet-Blondel method: hadronic final state

Reconstruction of event kinematics

Kinematics reconstructionKinematics reconstructionKinematics reconstructionKinematics reconstruction


Lines of constant electron energy (E’e)

Lines of constant electron angle (ϑ’e)

Lines of constant hadron energy (F)

Lines of constant hadron angle (γ)

Event kinematics (10GeV electron on 250GeV proton)



• Low-x-low Q2: Electron and current jet (low energy) predominantly in rear direction

• High-x-low Q2: Electron in rear and current jet (High energy) in forward direction

• High-x-high Q2: Electron predominantly in barrel/forward direction (High energy) and current jet in forward direction (High energy)

barrel

forward rear

Event topology (10GeV electron on 250GeV proton)Kinematics reconstructionKinematics reconstructionKinematics reconstructionKinematics reconstruction


Lines of constant electron energy

(E’e)

Lines of constant electron angle (ϑ’e)

Lines of constant hadron energy (F)

Lines of constant hadron angle (γ)

Event kinematics (5GeV electron on 50GeV proton)



• Low-x-low Q2: Electron and current jet (low energy) predominantly in rear direction

• High-x-low Q2: Electron in rear and current jet (High energy) in forward direction

• High-x-high Q2: Electron predominantly in barrel/forward direction (High energy) and current jet in forward direction (High energy)

barrel

forward rear

Event topology (5GeV electron on 50GeV proton)Kinematics reconstructionKinematics reconstructionKinematics reconstructionKinematics reconstruction


Electron method: scattered electron

Jacquet-Blondel method: hadronic final state

Resolution of event kinematics



Inclusive measurement - electron (Low x) and hadronic final state (High x) over wide acceptance range

Jet production and small-angle e tagger

In addition: p tagging in forward direction

Hermetic detector configuration / e- and e+ Missing energy measurement

K/π separation - particle ID - Heavy flavor - Secondary vertex reconstruction and J/Psi (Forward muons)

Forward acceptance: Tracking and calorimetry

Polarized ep physicsPrecision measurement of gp

1 over wide range in Q2

Extraction of gluon polarization through DGLAP

NLO analysis

Extraction of strong coupling constant

Precision measurement of gn1 (neutron) (Polarized

3He)

Photoproduction measurements

Electroweak structure function g5 measurements

Flavor separation through semi-inclusive DIS

Target and current fragmentation studies

Transversity measurements

eRHIC - Detector requirementseRHIC - Detector requirements


Inclusive measurement involving electron at small polar angles (≈10mrad)

Inclusive measurement involving electron (Low x) - Variable √s

Inclusive measurement (hadronic final state in forward direction): Good forward acceptance

Forward p tagging system

Similar to ep case at low x - High x: Forward acceptance - careful study necessary!

Forward p tagging system - photon/electron discrimination Variable √s and positrons

Unpolarized ep/eA physics Precision measurement of F2 at low x: Transition from hadronic to partonic behavior

Precision measurement of the longitudinal structure

function FL

Precision measurement of F2 at high x

Measurement of diffractive and exclusive reactions

DVCS

Precision measurement of eA scattering

eRHIC - Detector requirementseRHIC - Detector requirementseRHIC - Detector requirementseRHIC - Detector requirements


Detector specifications (1)

Tracking over wide acceptance range operating in high-rate environment - Contribute to reconstruction of event kinematics besides calorimetry in particular at very small energies

Calorimetry over wide acceptance range (e/h separation critical): Transverse and

longitudinal segmentation (Track-calorimeter cluster matching essential)

Specialized detector systems

Zero-degree photon detector (Control radiative corrections and luminosity

measurement)

Tagging of forward particles (Diffraction and nuclear fragments) such as…:

Proton remnant tagger

Zer0-degree neutron detector

Particle ID systems (K/π separation), secondary vertex reconstruction and muon system

(J/Psi)



ATLAS

Detector specifications (2)High-rate rate requirement

Background rejection: Timing requirements e.g. calorimetry timing essential to reject beam related background

Trigger: Multi-level trigger system involving

calorimetry and fast tracking information to enhance

data sample for rare processes over inclusive ep/eA

and photoproduction



Constrain on machine layout!

Constrain on machine layout!

General considerations: Detector aspects

Measure precisely scattered electron over large polar angle region (Kinematics of DIS reaction)

Tag electrons under small angles (Study of transition region: DIS and photoproduction)

Measure hadronic final state (Kinematics, jet studies, flavor tagging, fragmentation studies, particle ID)

Missing ET for events with neutrinos in the final state (W decays) (Hermetic

detector)

Zero-degree photon detector: Control radiative corrections and luminosity measurement (ep/eA Bremsstrahlung)


Proton remnant tagger

Zero degree neutron detector

Challenge to incorporate above in one detector: Focus on two specific detector concepts for now!

eRHIC - Detector design aspectseRHIC - Detector design aspectseRHIC - Detector design aspectseRHIC - Detector design aspects


Ae

e

A

General considerationsDesign 1: Forward physics (unpolarized eA MPI Munich group):

Specialized detector system to enhance forward acceptance of scattered electrons and hadronic final state

Main concept: Long inner dipole field (7m)

Required machine element-free region: approx. 5m

• Design 2: General purpose (unpolarized/polarized ELECTRon-A):• Compact central detector (Solenoidal magnetic field) with specialized

forward/rear tagging detectors/spectrometers to extend central detector acceptance

• Required machine element-free region: approx. 3m

Detector sub-systems in both design concepts:Zero-degree photon detector (Control radiative corrections and luminosity measurement)


Proton remnant tagger / proton spectrometer Zer0-degree neutron detector

eRHIC - Detector design aspectseRHIC - Detector design aspects


Design 1: Forward physics (unpolarized eA MPI-Munich group) (1)

Detector conceptCompact detector with tracking and central EM calorimetry inside a magnetic dipole field and calorimetric end-walls outside:

Bend forward charged particles into detector volume

Extend rapidity compared to existing detectors

Tracking focuses on forward and backward tracks

No tracking in central region


I. Abt, A. Caldwell, X. Liu, J. Sutiak, MPP-2004-90, hep-ex 0407053


Tracking system:

•High-precision tracking with ΔpT/pT ~ 2%

•Angular coverage down to η ≈ 6 over the full energy range

•Concept: 14 Si-strip tracking

stations (40 X 40 cm)

•Assumed hit resolution: 20μm

•Momentum resolution from

simulations: Few percent!





Calorimeter system:

•Compact EM calorimeter systems: Si-Tungsten

•Forward hadron calorimeter: Design follows existing ZEUS calorimeter






Track efficiency:

• Full efficiency below 6GeV for η > -8

• For larger energies, full efficiency for η > -5


Acceptance:Full tracking acceptance for |η| > 0.75 - No acceptance in central region |η| < 0.5

Q2 acceptance down to 0.05GeV2 (Full W range) - Full acceptance down Q2=0GeV2 for

W>80GeV

High x: Electron (Q2) and Jet (x) to determine event kinematics



J. Pasukonis, B.S.

Detector concept:

•Hermetic detector system inside ±3m

machine element free region

•Starting point:

Barrel and rear EM system: e.g. Si-Tungsten

(Similar to Design 1)

Forward EM/hadron calorimeter: e.g. Pb-

scintillator

Tracking system and barrel EM inside

solenoidal magnetic field

Tracking system based on high-precision Si

(inner) and micro-pattern technology (Triple-

GEM) (outer)

Ae

Design 2: General purpose (unpolarized/polarized ELECTRon-A) (1)




ELECTRA detector simulation and

reconstruction framework:

GEANT simulation of the central detector part

(tracking/calorimetry) available: Starting point

Calorimeter cluster and track reconstruction

implemented

Code available through CVS repository:

• http://

starmac.lns.mit.edu/~erhic/electra/

To-do-list:

Evaluate and optimize detector configuration

- In particular: Type of magnetic field

configuration

Design of forward tagging system and

particle ID systems

Rear detection systems

For eA events: Optimize forward detector

system for high-multiplicity environment

eRHIC - Detector design aspectseRHIC - Detector design aspectsJ. Pasukonis, B.S.


DIS generators

used so far: LEPTO DJANGO

Lower Q2

acceptance ≈

0.1GeV2

Side view


Simulated ep DIS event (LEPTO)

eRHIC - Detector design aspectseRHIC - Detector design aspectsJ. Pasukonis, B.S.


E. Kistenev



IR region

Design concept: Forward physics (unpolarized eA MPI-Munich group)

Machine element free-region: approx. 5m

Physics program could be accomplished at lower luminosity

Design concept: General purpose (unpolarized/polarized ELECTRon-A)

Machine element free-region: approx. 3m

Physics program requires high luminosity operation

Synchrotron radiation background

Optimize beam pipe shape

Accommodate synchrotron radiation fan generated by e-beam as a result of beam separation

Maximize detector acceptance

Design of absorber and masking system

Beam-gas background

Bremsstrahlung of electrons with residual gas and proton-beam gas background

Shielding and collimation

Minimize dead-material close to the beam

Good vacuum conditions crucial



Preparation of eA case:

eA MC generators:

VNI (Not tested - requires comparison to LEPTO)

Can we get VENUS?

Incorporate saturation effects in existing MC generators?

ELECTRA: Detector simulation and reconstruction framework available

Kinematic reconstruction:

Low x : Electron

High x: Use hadronic final state. How well does this work for eA?

Multiplicity eA vs. ep, in particular in the forward direction?

Luminosity measurement?

Simulation of F2A? Which range in A?

Beyond F2A: FL and VM production

Global analysis of gluon distribution function

Concluding remarksConcluding remarks


Critical eRHIC R&D issues

Calorimetry: Compact, high resolution, e/h separation

Tracking: High-rate, low dead material, high occupancy (Forward

direction)

Forward/Rear instrumentation: Compact, high radiation environment

Magnetic field configuration: Combination of solenoid and dipole-type

configuration

DAQ/Trigger system: Multi-level trigger system

Background: Synchrotron radiation absorber and shielding



ep/eA(Represented by two leaders in DIS/Rel.Heavy Ion)

: Several participating institutes chaired by 2 conveners

CalorimetryCalorimetry

TrackingTrackingMagnetic fieldMagnetic field

Particle IDParticle ID

IR interface

Trigger/DAQTrigger/DAQ

Rear tagging systemRear tagging system

MC

Polarimetry (e/p)

Forward tagging systemForward tagging system



ZEUS UCAL Module design

Depleted Uranium-Scintillator Calorimeter

• 3.3 mm DU plates clad in stainless

steel

• 2.6 mm scintillator

• e/h = 1 (EM response = hadronic)

• Compensating (energy from neutrals)

18 % / √E - Electromagnetic resolution

35% / √E - Hadronic resolution

Timing resolution: 1.5ns / √E

• Modules 20cm wide

Various heights: 220 - 460cm

Coverage and depth:

Forward (FCAL): (7λ): 2.2° - 39.9°

Barrel (BCAL): 36.7° - 129.1°

Rear (RCAL): (4λ): 128.1° - 176.5°

Hadronic CalorimetryHadronic Calorimetry


Details on ZEUS UCAL dismantling and handling

Formal agreement between DESY and DOE that UCAL has to be shipped back to the US (DOE owns U material)

Shipping costs will be covered by DESY and DOE

Current plan in case of no further usage:

Shipment on container ship without further pre-caution of further re-usage (Transport several modules

in one container)

Quotations are currently being discussed with several companies in Germany

Shipment will be carried out to Utah under supervision of ANL and DOE

Handling of UCAL modules in Utah will be carried out by a DOE contractor for long-term underground

storage

Dismantling of the ZEUS detector will start in July 2007

Current plan: Dismantle UCAL modules first with short-term storage in ZEUS experimental hall

Subsequent shipment of modules to US (Utah) over the course of < 1 year



Note to BNL management under preparation by MIT group

Excellent instrument which is fully functional with the best hadronic energy

resolution

Idea: Re-use ZEUS UCAL for the forward hadronic calorimeter

Note: Uranium material belongs to DOE and has to be shipped back the US

Part to achieve a cost effective solution for a detector at eRHIC

Shipment has to be carried out differently than in case of no further usage:

One module per container

Special transport frames and shock absorbers

Difference in cost compared to no further usage



Expression of interest: Transport ZEUS UCAL modules to BNL for EIC

Decide on FCAL/RCAL modules for optimal coverage

Transport frames could be assembled at MIT-Bates

Coordination: D. Hasell (MIT)

Difference in cost compared to no further usage would have to be covered by BNL (< $100k)

Agreement from DESY and ZEUS management: Local engineering help will be provided by

ZEUS for storage and transport to container ship (Compensation: 1-2 technicans for period

of 1-2 months)

Shipment of UCAL modules to BNL

Locate area in AGS experimental hall area for storage and test over several years

Test and evaluation of performance under leadership of MIT (Coordination: D. Hasell)

Note: Cost factor $20M (~1990) (Inflation (2005): $30M) (No labor cost included!). Including

labor cost assuming a factor 2 would result in: $60M (2005): ZEUS modules will be provided

at no further cost!


overview oferhic detector design studies

Documents

nucleus structure

nucleon structure

parton densities

parton j

functions of q2

parton of type

fldis kinematics

quarkparton model