snowmass 14-7-01g. eigen, university of bergen g. eigen university of bergen snowmass july 14, 2001

Snowmass 14-7-01 G. Eigen, University of Bergen

G. EigenUniversity of BergenSnowmass July 14, 2001


OUTLINEOUTLINE

Introduction

Silicon Vertex Detectors

Drift Chambers

DIRC

Electromagnetic Calorimeters

IFR

Trigger Rates

Examples of strawman detectors

Conclusion


IntroductionIntroduction

For precision measurements of CP-violation asymmetries and rare B decays high luminosities are an important prerequisite

Recently, the design of an e+ e- storage ring s ~ 10GeV with luminosities of £peak = 1036 has become feasable

So how do present subsystems of multipurpose detectors cope with the increased background levels ? The following results are my personal views based on BABAR studies: Report of the High-Luminosity Background Task force (C. Hast, W. Kozanecki (chair), A. Kulikov, T.I. Meyer, S. Petrak, T. Schietinger, S. Robertson,M. Sullivan, J. Va’vra, BaBar Note 522)

Results for £peak ≥ 1035 should be taken with a grain of salt: Extrapolations are made over > 2 orders of magnitude (errors > factor 2) Extrapolations depend very much on IR layout


Background IssuesBackground Issues

Acceptable levels of backgrounds are determined by

Radiation hardness of subdetectors inefficiencies, destruction

Trigger rate deadtime, loss of signal

Detector occupancies inefficiencies, worse resolution, worse S/B

Occupancy and trigger rate determine acceptable dynamic running conditions

Total integrated radiation dose determines lifetime of subdetectors

Dose is accumulated under normal running conditions, during injection, machine studies and beam-loss events At PEP II dose accumulated during running dominates At £peak = 1036 machine this is different, injection losses determine dose

Present Measures of BABAR Subsystems to Present Measures of BABAR Subsystems to Machine BackgroundsMachine Backgrounds

Radiation Hardness of SVT detector modules is estimated at 2MRad Instantaneous dose rate in radiation protection diodes BW:MID & FE:MID are within factor of two representative of harshest radiation levels hitting SVT modules in horizontal plane Total current drawn by drift chamber is limited to 1000 A by existing HV power supplies

Counting rate above 200-300 kHz in DIRC phototubes starts inducing significant dead time with present electronics

Fractional EMC crystal occupancy above a 1 MeV threshold and number of crystals above 10 MeV characterize potential degradation of calorimeter energy resolution, as well as number of fake neutral clusters

Level-1 (L1) trigger rate is currently limited to 2.0-2.5 kHz by DAQ bandwidth considerations


Present Sources of Machine BackgroundsPresent Sources of Machine Backgrounds

Detector subsystems are subjected to different machine-related backgrounds

Electrons: lost particles backgrounds (beam-gas bremsstrahlung, Coulomb scattering) and synchrotron radiation

Positrons: lost particles backgrounds (beam-gas bremsstrahlung)

2 beams: no collision single beam backgrounds above plus beam-gas cross term in collision backgrounds from luminosity, beam-beam tails & above 3

Note that there is a difference in operation between PEP II at high £peak & an £peak = 1036 collider: PEP II: inject & run (stable beams) continuous injection (no stable beams)


Backgrounds in PEP II & in an L=10Backgrounds in PEP II & in an L=103636 Machine Machine

Background estimates by W. Kozanecki based on J. Seeman’s design PEP II 1036

Beam loss rates in PEP II and a 1036 machine differ by a factor of > 103

but only small fraction will contribute to detector backgrounds

HER LER Super HER Super LER

Beam current Ib [A] 0.7 1.4 5.5 20.5

Beam lifetime b [min] 550 150 4.2 3.2

Beam loss rate Ib/ b

Luminosity [A/min] 0.37 0.35

Vacuum [A/min] 0.06 0.68

Touschek [A/min] 0.06 2.28

b-b tune shift [A/min] 0.55 2.05

Dynamic aperture [A/min] 0.28 1.03

Total [A/min] 1.310-3 9.310-3 1.32 6.39


Backgrounds in an L=10Backgrounds in an L=103636 Machine Machine

In PEP II LER lifetime is dominated by vacuum or Touschek effect, while HER lifetime is affected by beam-beam tune shift and then vacuum Background sources in SVT, DCH and EMC result from beam-gas in the incoming straight section

Beam-beam tune shifts, dynamic aperture and vacuum losses probably will contribute to vacuum-like backgrounds, since losses are transverse (like distant LER Coulomb scattering in PEP II)

Since quads need to be shielded transverse losses are produced at betatron collimators far from IP combined transverse losses are main issue with LER backgrounds only 15%-20% of them, HER is minor problem

Effects of longitudinal losses at £peak = 1036 are not known, since these have not been studied in PEP II

Since sum of longitudinal, all transverse and injection losses is so large, vacuum in IR will be less a problem, still need pressure of 10-9 within 50m of IP


Dependence of backgrounds on beam currentsDependence of backgrounds on beam currents

Touschek: Dependence is not known, expect no effect for a while (low ILER, long Touschek lifetime, negligible secondary particles) At some point it will take off need simulation with Turtle

Beam-beam tune shift: very non-linear and very tune sensitive

Dynamic Aperture: linear (?)

Vacuum: quadratic in ILER (the base pressure will be well-controlled, the dynamic pressure will dominate)

Luminosity: linear in beam currents


Estimates of backgrounds due to beam lossesEstimates of backgrounds due to beam losses

Touschek: Need Turtle-like simulation of energy spectrum

Tranverse losses: Scale distant Coulomb prediction by the ratio of loss rates with measured distant LER-only contributions (DCH,DIRC)

Injection losses: Take clean injection day from PEP II and scale by injection currents

Secondary particles: Due to multistage injection, betatron collimation and momentum collimation secondary particles are big issue realistic simulation is a major task

Radiative Bhabha: Debris in the detector from radiative Bhabhas eventually will become large, it is sensitive to beam line geometry & IR layout

Caution: In extrapolations below none of above effects is included

Multipurpose Detector for e+e-Collisions at 10GeVMultipurpose Detector for e+e-Collisions at 10GeV


Luminosity ConsiderationsLuminosity Considerations

For luminosities shown in blue extrapolations have been taken from the report of the High-Luminosity Background Task force, while for luminosities shown in green results are my extrapolations using the algorithms given by the High-Luminosity Background Task force

Date £peak [cm-1 s-1]

June 2002 6.51033

August 2005 1.51034

2008 ? 5.01034

? 1.01035

1.01036


Silicon Vertex TrackersSilicon Vertex Trackers


Dose accumulated in BABAR SVTDose accumulated in BABAR SVT


SVT Radiation Dose in Middle PlaneSVT Radiation Dose in Middle Plane

time

SV

T d

ose

rate

[k

rad

/y]

21033 1034 5 1035 5 1036

FE MIDBW MID

SVT dose rate: FE MID [kRad/y] =128 ILER + 16 I2LER

BW MID [kRad/y] =246 IHER + 9.1 I2HER

In top & bottom planes dose rate is ~ factor of 10 lower than in middle plane


Silicon Vertex Detector OccupancySilicon Vertex Detector Occupancy


Conclusion on Silicon Vertex DetectorsConclusion on Silicon Vertex Detectors

Radiation levels depend very strongly on IR layout, (KEKB < PEP II)

In BABAR silicon detectors are expected to survive a total dose of 2MRad With replacements of detectors in the MID plane BABAR SVT is expected to survive luminosities of 1.5-31034

LHC R&D demonstrated that Si detectors can survive high irradiation H. Yamamoto bonded 150 thick pixels (55 55 ) (CMOS)

At £peak ~ 11036 occupancy is an issue for Si strip detectors close to IR pixels in first two layers

So for £peak ~ 1-101035 appropriate silicon detectors probably work

£peak [cm-1 s-1] 6.5103

3

1.51034 51034 11035 11036

∫£dt [fb-1]/y 65 150 500 1000 10000

ILER/ IHER [A] 2.8/1.1 3.7/1.3 4.6/1.5 9/2.5 18/5.5

DSVT [kRad/y] 480/280 690/ 340 1300/470 2450/670

7490/1630


Drift ChambersDrift Chambers


Machine backgrounds affect operation of Drift Chamber in 3 ways: Total current IDCH in Drift Chamber drawn by wires is dominated by charge of beam-related showers IDCH is limited by high-voltage system, above limit chamber becomes non operational! high currents also contribute to aging of chamber! maximum Qmax: 0.1-1.0 Cb/cm of wire Occupancy in Drift Chamber due to backgrounds (hits, tracks) can hamper reconstruction of physics events

Ionization radiation can permanently damage read-out electronics & digitizing electronics

Drift ChambersDrift Chambers


Drift Chamber CurrentsDrift Chamber Currents

IDCH [A] = 35.3 ILER +23.5 I2LER + 77.2 IHER +46.3 I2

HER + 41.9 £ -14 with currents in [A] and luminosity in units of [1033 cm-1 s-1]

Single beam and collision measurements taken June/ July at HV=1900V

For HV=1960V scale current by factor 1.67


Measured Drift Chamber Currents & ModelsMeasured Drift Chamber Currents & Models

Single-beam measurements (LER) taken with BABAR DCH in June and July 2000 at HV=1900V


Drift Chamber BackgroundsDrift Chamber Backgrounds

Extrapolation for HV=1900V

At HV=1960 background levels are expecetd to be 65% higher

time

tota

l D

CH

cu

rren

t [

A]

21033 1034 5 1035 5 1036

LuminosityILER

IHER


Drift Chamber OccupancyDrift Chamber Occupancy

NDCH = 0.044+0.191 ILER +0.0402 I2LER + 1.03 IHER +0.113 I2

HER + 0.147 £ with occupancy in [%], currents in [A], luminosity in units of [1033 cm-1 s-1] at 1900V

At HV=1900V (Jan-July): NDCH = 158+0.27 IDCH (<350A)

At HV=1960 V(July-now): NDCH = 203+0.18 IDCH (>200A)

Large spread extrapolation difficult

data points at ~ same £


Drift Chamber OccupancyDrift Chamber Occupancy

Extrapolation for HV=1900V

time

DC

Hoc

cup

ancy

t [%

]

21033 1034 5 1035 5 1036

LuminosityILER

IHER

NDCH = 0.044+0.191 ILER +0.0402 I2LER + 1.03 IHER +0.113 I2

HER + 0.147 £


Conclusion on Drift ChambersConclusion on Drift Chambers

Total dose depends on ∫£dt: at 20 fb-1 accumulated 100 rads

For £peak > 11035 it is very unlikely that drift chambers will work One needs other devices: straws, TPC with GEM readout, Si tracker

£peak [cm-1 s-1] 6.5103

3

1.51034 51034 11035 11036

∫£dt [fb-1]/y 65 150 500 1000 10000

ILER/ IHER [A] 2.8/1.1 3.7/1.3 4.6/1.5 9/2.5 18/5.5

IDCH [A] 680 1250 3370 6880 51960

NDCH [%] 3.1 5 12 23 173

Qwire [mCb] ~15 36 100 200 2000


GEM LayoutGEM Layout


DIRC DIRC

PARTICLE IDENTIFICATIONPARTICLE IDENTIFICATION


Composition of DIRC BackgroundComposition of DIRC Background

time

DIR

C o

ccu

pan

cy [

kH

z]21033 1034 5 1035 5 1036

NDIRC [kHz] = 35 ILER + 8.5 IHER + 25 £

totalILER

IHER


Conclusion on DIRCConclusion on DIRC

BABAR DIRC is ok up to £peak =61034, however the water tank provides a huge Cherenkov detector

At high luminosities £peak >11035 another approach is needed: a compact readout using focussing or timing

£peak [cm-1 s-1] 6.5103

3

1.51034 51034 11035 11036

∫£dt [fb-1]/y 65 150 500 1000 10000

ILER/ IHER [A] 2.8/1.1 3.7/1.3 4.6/1.5 9/2.5 18/5.5

NDIRC [kHz] 270 516 1470 2840 25700


Different DIRC Imaging Methods

Note that different imaging methods can be chosen in each space dimension


DIRC Readout

B. Ratcliff


Separation Performance vs Random Rates


ELECTROMAGNETICELECTROMAGNETIC

CALORIMETERCALORIMETER


Average Occupancy in EMC CrystalsAverage Occupancy in EMC Crystals

NEMC (E> 1MeV)= 9.8 + 2.2 IHER +2.2 ILER + 1.4 £ NEMC (E> 10MeV)= 4.7 IHER + 0.23 I2

HER +2.4 ILER + 0.33 I2LER + 0.6 £

with beam currents in units of [A] and luminosity in units of [1033 cm-1 s-1]

Single Crystaloccupancy

# Crystalswith > 10 MeV


Light Yield Changes in EMCLight Yield Changes in EMC


Worst Dose Rate in EMCWorst Dose Rate in EMC


Effect of Background on Effect of Background on 0 0 ReconstructionReconstruction

Background photons both increase 0 background levels and degrade mass resolution


time

21033 1034 5 1035 5 1036

Composition of EMC BackgroundsComposition of EMC BackgroundsE

MC

occ

up

ancy

t [%

]

time#

EM

C c

ryst

als

> 10 MeV

totalILER

IHER

21033 1034 5 1035 5 1036

> 1 MeV


HER +2.4 ILER + 0.33 I2LER + 0.6 £

totalILER

IHER

noise

Conclusion on Electromagnetic CalorimetersConclusion on Electromagnetic Calorimeters

For luminosities < 1.51034 integrated radiation dose for CsI(Tl) crystals is not expected to be a problem if observed light losses scale as expected

Impact of large number of low-energy photons on EMC energy resolution depends on clustering algorithm, digital filtering, etc (needs further study) Expect luminosity contribution to be dominant

Expect reduction of background rates through improvements of vacuum near IR combined with effective collimation against e+ from distant Coulomb scattering

For luminosities >11035 light loss due to radiation and occupancy levels for present CsI(Tl) crystals are not acceptable need R&D studies and look into other scintillator (pure CsI, LSO, GSO?)

£peak [cm-1 s-1] 6.5103

3

1.51034 51034 11035 11036

∫£dt [fb-1]/y 65 150 500 1000 10000

ILER/ IHER [A] 2.8/1.1 3.7/1.3 4.6/1.5 9/2.5 18/5.5

NEMC [%] 28 42 93 175 1460

Ncluster 21 32 56 122 783


Properties of Scintillating CrystalsProperties of Scintillating Crystals


INSTRUMENTED FLUX RETURNINSTRUMENTED FLUX RETURN


Conclusion on IFRConclusion on IFR

Main issue is high occupancy in outer layers due to beam-related backgrounds

Presently outer RPC layer has random occupancy of several %

At design currents and at higher luminosity this will become an unacceptably high contribution to / misidentification

Solution for £peak ~ 3-51034 : build 5 cm thick Fe shield following outer-most chamber

At £peak > 11035 occupancy becomes an issue despite shielding RPC’s are not suited, replace them with scintillating fibers


TRIGGERSTRIGGERS


L1 Trigger Rate vs Current in MachineL1 Trigger Rate vs Current in Machine


Trigger RatesTrigger Rates

time

Tot

al t

rigg

er r

ate

[Hz]

21033 1034 5 1035 5 1036

Total (L)IHER

ILER

Background

Expected L1 trigger rate: L1 [Hz]=130 (cosmics)+ 130 ILER + 360 IHER + 70 £


Extrapolation on Trigger RatesExtrapolation on Trigger Rates

For £peak ~1.51034 in BABAR trigger needs to be upgraded to cope with high rates

For higher luminosities one could do more stringent prescaling of Bhabhas, radiative Bhabhas, beam gas, (want to keep all b, c decays) One needs to design appropriate tracking device used in trigger

LHC experiments can accept L1 trigger rates of 100 kHz (ATLAS) bunch crossing is 40 MHz

£peak [cm-1 s-1] 6.5103

3

1.51034 51034 11035 11036

∫£dt [fb-1]/y 65 150 500 1000 10000

ILER/ IHER [A] 2.8/1.1 3.7/1.3 4.6/1.5 9/2.5 18/5.5

L1 [Hz] 1350 2130 4800 9200 74500


Trigger for High Luminosity MachineTrigger for High Luminosity Machine

Detector ConsiderationsDetector Considerations

The angular acceptance is limited by beam focussing elements to 300mr

By keeping present boost =0.58 and a resolution improved by a factor of two one needs to move closer to IP 1cm gold-plated Be beam pipe

To cope with occupancy problems near IR, use Si pixel detectors for first 2 layers of vertex detector, 3 layers Si strip detectors

For central tracker consider either all Si strips, straw tubes or TPC with GEMs readout

For particle identification consider Super DIRC

For EMC consider scintillating crystal calorimeter based on pure CsI, LSO or GSO

For IFR use Fe plates read out with scintillating fibers

Strawman designs resulted in discussions in breakout sessions: G. Dubois-Felsman, G. E., M. Giorgio, D. Hitlin, X. Lou, D. Leith, E. Paoloni, I. Peruzzi, M. Piccolo, M. Sokoloff, H. Yamamoto


Modified Multipurpose DetectorModified Multipurpose Detector

TPC with GEMs ECsor strawtubes

Pure CsI withAPD’s readout

Compact DIRC

IFR with scintillating fibers

First 2 layerspixels +3 layersSi strips


Compact Multipurpose DetectorCompact Multipurpose Detector

SVT 2 Ly pixel3 Ly Si strip

4 Ly Si striptracker

Compact DIRC

LSO EMC

3T Coil

IFR Fe + scint. fibers


ConclusionsConclusions Vertex detectors:

Based on studies at LHC silicon vertex detectors probably will work at high luminosties of £peak ~ 1-101035, need pixel detectors in first two layers ( R & D) Central tracker:

For £peak > 11035 it is very unlikely that drift chambers will work Need to consider an all Si strip tracker, straw tubes or TPC/GEMs

Particle ID: With appropriate design of accepted counting rates, beam collimation & shielding a compact DIRC probably will work at £peak ~ 1-101035

Electromagnetic Calorimeter: For £peak >11035 light loss due to radiation and occupancy levels for

present CsI(Tl) crystals are not suitable explore other scintillators (pure CsI, LSO, GSO,…) ( need R&D)

Trigger: It should be possible to design trigger system for £peak = 11036


Silicon Vertex Detectors


L1 Trigger Rate vs Current in Machine


Drift Chamber Currents


Average Occupancy in EMC Crystals

Single Crystaloccupancy

# Crystalswith > 10 MeV


HER +2.4 ILER + 0.33 I2LER + 0.6 £

with beam currents in units of [A] and luminosity in units of [1033 cm-1 s-1]

snowmass 14-7-01g. eigen, university of bergen g. eigen university of bergen snowmass july 14, 2001

Documents

dose slide

collision backgrounds

beambeam tails

high peak

machine studies

luminosities of peak

l1 trigger rate

beamloss events