Äîêóìåíò âçÿò èç êýøà ïîèñêîâîé ìàøèíû. Àäðåñ îðèãèíàëüíîãî äîêóìåíòà : http://zebu.uoregon.edu/~uochep/talks/talks02/NLC02_RD.pdf Äàòà èçìåíåíèÿ: Fri Mar 14 02:05:58 2003 Äàòà èíäåêñèðîâàíèÿ: Tue Oct 2 10:50:43 2012 Êîäèðîâêà: Ïîèñêîâûå ñëîâà: m 5

Linear Collider Beam Instrumentation Overview
Linear Collider R&D Opportunities Workshop May 31st, 2002 SLAC Eric Torrence* University of Oregon *with M.Woods and D.Cinabro · BI Overview · Beam Energy · Polarization · Luminosity
http://physics.uoregon.edu/~torrence/talks/
Eric Torrence 1/27 May 2002


BI Overview

Beam Instrumentation Topics · Beam Energy Scale and Width · Beam Polarization · Integrated Luminosity and Spectrum Instrumentation needed for physics...

State of Affairs · Many conceptual ideas · Few concrete designs or detailed studies · First meeting of new study June 26th
http://www.slac.stanford.edu/~torrence/ipbi/

Significant Overlap · Detector/Physics groups · Beam delivery/Final focus activities · Accelerator instrumentation

Eric Torrence

2/27

May 2002


Beam Energy at LEP II Production Threshold
[pb]
WW

LEP
20
RacoonWW / YFSWW 1.16

Preliminary

15

10
18

YFSWW 1.16 RacoonWW

5

17

16

0

160

170

180
E
cm

[GeV]

190

200

210

Kinematic Fits

3500 3000 2500 2000
Hadronic Mass

WW ¡ qql
2C Kinematic Fit

1500 1000 500 0 40 50 60 70 80 90 100 Invariant Mass (GeV) M W E Beam ------------ -----------------MW E Beam
May 2002

Common Scale Uncertainty
Eric Torrence 3/27


Polarization at SLC Hadronic Final States
N ­N L R 1 A LR = ----- ---------------------Pe N L + N R

Leptonic Final States

events

600 500 400 300 200 100 0

Z µ µ 97-98

0

+-

e e

-R L
-0.6 -0.4 -0.2 0 0.2 0.4

SLD
0.6

-0.8

cos

0.8

Combined sin
2 eff W

= 0.23098 ± 0.00026

Still statistics limited...
Eric Torrence 4/27 May 2002


Linear Collider Requirements Beam Energy Scale · mt from tt threshold · mH from direct reconstruction · mnew from either E b / E b ~ 100-200 ppm Polarization · SM asymmetries ( l + l -, qq, WW , ...) · Background suppression of WW · SUSY quantum numbers P / P ~ 0.25 - 0.5% Luminosity Spectrum · mt from tt threshold · most every physics result! (at some level) Know dL / dE ~ 1% Very challenging in LC environment!
Eric Torrence 5/27 May 2002


GigaZ Requirements Weak Mixing Angle
sin
2 eff W

E

beam

P- / P

-

P

eff

/P

eff

SLD

0.00026 25 MeV

0.50% 0.25% 0.25%
P-

e- only 0.00005 ~ 5 MeV Blondel 0.00002 ~ 2 MeV

0.10%

NL ­ NR 1 A LR = ---------- ---------------------- where P eff P eff N L + N R

+ P += ------------------1 + P-P+

WW Threshold m
W

~ 6 MeV E b < 5 MeV

Also Needed · Low beamstrahlung (separate IP) · Positron polarization · Theory improvements Very challenging for BI!
Eric Torrence 6/27 May 2002


General Issues

Measurement time scales · · · · Luminosity averaged Operator tuning Train-to-train Bunch-to-bunch months minutes 10 ms 1 ns

Correlations between L, E, P need to be understood Measurement Location · At IP (luminosity weighted) · Near IP in final focus (upstream/downstream) · Elsewhere in machine Measurement Frequency · Every pulse - in collision · Sampled (dropouts?) · Dedicated runs How much time needed for calibration?

Must compare physics needs to operational needs...
Eric Torrence 7/27 May 2002


Linear Collider Beam Energy Measurements (E. Torrence)

Eric Torrence

8/27

May 2002


Energy Overview

Energy needs · 100-200 ppm absolute energy scale · pulse-by-pulse relative measurement? · Detailed width measurement also Can calibrate at Z-pole ~ yearly?

Potential beam methods · WISRD-style spectrometer · LEP-style BPM spectrometer · MÜller/Bhabha scattering target ·`Wire' scanner at high dispersion · Your good idea???

Potential detector methods · Radiative return ( µ + µ - ) kinematics · Mu-pair momenta?

Eric Torrence

9/27

May 2002


Meet the WISRD
Spectrometer Magnet Quadrupole Vertical Doublet eHorizontal Bends for Synchrotron Radiation

E

beam

l = -- B dl x



Dump Synchrotron Light Monitor

e+



B dl = 3.05 T m

l = 15 m x = 27 cm at 50 GeV

Systematic Errors per Beam
B dl : Alignment: 190 ppm Detector - IP: 135 ppm Total: 250 ppm 12.5 MeV at 50 GeV 1998 SLC mZ scan implies a ~ 40 ± 20 MeV offset in ECM



100 ppm

NLC Questions · · · · Stronger bend (and where)? Better detector technology Possible downstream (in collision)? Also measure energy shape?
10/27 May 2002

Eric Torrence


BPM Spectrometer

LEPII Spectrometer · · · · Relies heavily on frequent calibrations 1 micron stability for less than 8 hours Operated within tight dynamic range Beam position and bend held constant

Very low duty factor for LC operations

RF Spectrometer
RF BPM Triplets

~1 meter

· Compact 1m RF BPM triplet blocks · Chicane layout for better alignment control · Magnet system more complicated 100 nm precision required... (assuming 1 mRad bending)
Eric Torrence 11/27 May 2002


MÜller Scattering
Silicon Microstrip Detector (SMD) Hydrogen Gas Jet (GJT) Scattered electron 1 LEP beam Recoil Proton Tracker 2 Electromagnetic Calorimeter (ECAL) E1

L

E2

E

beam

8 me 1 = ----------------------------------------- -------------- ­ m ( tan 1 + tan 2 ) 2 1 ­ 2

e

tan 1 ­ tan 2 E1 ­ E2 = --------------------------------- or = -----------------tan 1 + tan 2 E1 + E2 · Use angles only (need IP position) · Use energy and angles (independent of IP position)

LEP II Study

[LEP II Yellow Report]

l = 30 meters = 2 ­ 6 mRad angular acceptance E / E = 3.37 / E ( GeV ) 1 / 4 % resolution

E E

stat syst

= 2 MeV in 30 minutes (~600 Hz) 2 MeV (dominated by Fermi motion)

Complete study for LC needed...
Eric Torrence 12/27 May 2002


Radiative Returns at LEP f e+e- ¡ f f Statistics
Channel Ebeam

1 f
Number of Events / 1 GeV

2

sin 1 + sin 2 ­ sin ( 1 + 2 ) s' -- = -----------------------------------------------------------------------sin 1 + sin 2 + sin ( 1 + 2 ) s

300

Data qq M.C. reweighted M.C. background 183 GeV Data MZ = 91.172 ± 0.098 GeV

L3

qq µµ ee

~ 18 MeV ~ 40 MeV ~ 70 MeV

200

LEP Potential Statistics Only 2.7 fb-1

100

0 70

80

90

100

110

m

inv

[ GeV]
Estimates Ebeam ~ 70 MeV Ebeam ~ 20 MeV Ebeam ~ 80 MeV
May 2002

Systematics
· Theoretical Description · Hadronization Uncertainties · Detector Understanding Need absolute measurement!
Eric Torrence 13/27

Opal qq µµ ee


Radiative Returns at NLC
cos 1 0.9 0.8 0.7 0.6 0.5 200 300 400 500 600 800 1000 Collision Energy (GeV)
2 Symmetric production: s = m Z , 1 =

e+e- ¡ µµ

1 2

2

Collision Energy 2 mW 2 mt 500 GeV 1 TeV

cos 0.522 0.875 0.937 0.984

(mRad) 1000 500 360 180

Need precision and accuracy at small 0. 1 % per event ( Z limit)
Eric Torrence 14/27 May 2002


Linear Collider Polarimetry (M. Woods)

Eric Torrence

15/27

May 2002


Polarimetry Overview

Polarization Needs · P / P ~ 0.25 - 0.5% · Each helicity state separately · In vs. out of collision difference? e+ polarization a big help!

Location and Technology · · · · · Source Damping ring DR - IP Interaction point Post IP Mott scattering Synchrotron? Laser Wire? WW pairs or Blondel (e+) Compton scattering

Other issues · Significant depolarization during collisions · In-collision measurements desired · Post-IP environment very difficult
Eric Torrence 16/27 May 2002


Compton Polarimetry
532 nm Frequency Doubled YAG Laser e­ Mirror Box Pockels Cell Left or Right Circularly Polarized Photons Focusing and Steering Lens Mirror Box (preserves circular polarization) Compton Back Scattered e­ Analyzing Bend Magnet
1-93 7268A1

e+

SLD e­ Laser Beam Analyzer and Dump "Compton IP"

Cerenkov Detector Proportional Tube Detector

Multiple Detectors ·ãerenkov counter - scattered e- asymmetry · Photon counter - integral E asymmetry · Quartz fiber calorimeter - transverse asym. Unique systematics help reduce errors

Eric Torrence

17/27

May 2002


ãerenkov Detector
Preradiator 7 mm Pb

Window 0.5 cm Al

Electron (Beam Pipe)

Cherenkov Detector

Proportional Tube Detector 250 µm Al walls in radiator region. All reflective
surfaces coated with 1000 å pure Al

45° Al coated Stainless Mirrors Phototubes (Hamamatsu R1398)

Pb Shielding
10-92 7268A6

Eric Torrence

18/27

May 2002


NLC Polarimetry Goals Uncertainty Source Analyzing Power Detector Linearity Laser Polarization Electronic Noise Total Uncertainty IP Corrections Improvements · Better segmentation in Cherenkov counter · Better design to define active volume · Additional e- detectors? Kinematics at high energy are favorable! Outstanding Issues · Extraction line design · Background tolerance · NLC bunch structure/timing 1-2% depolarization in collision process!
Eric Torrence 19/27 May 2002

P / P SLD 0.40% 0.20% 0.10% 0.20% 0.50% 0.15%

P / P LC 0.20% 0.10% 0.10% 0.05% 0.25% < 0.05%


Depolarization Effects
Depolarization [%]

60

40

P vs. Efinal
K. Thompson January 2001 SLAC PUB 8716
100 200 300 400 500 Electron energy [GeV]

20

0

P vs. y /

y

3 2 1

Total Outgoing Bunch Lumi weighted ~ 25% of bunch average P Lumi Weighted How well can this be determined???
Eric Torrence 20/27

0

0

5

10

15

3 2 1 0 0 5 10 15
May 2002

S-T BMT

Total


Direct Polarization

W

Z/

W



W W

= 12 ­ 7 pb at s = 350 ­ 500 GeV
ALR

1

0.8

s = 800 GeV

0.6

= 1.007 Z = 1.01 SM

0.4

-1

-0.5

0

0.5

1 cos

[K. MÆnig, Snowmass 2001]

P / P < 0.1 % for 500 fb-1 at 350 GeV (9/1 L ratio) Similar with e- only
Eric Torrence 21/27 May 2002


Linear Collider Luminosity Issues (D. Cinabro)

Eric Torrence

22/27

May 2002


Luminosity Overview

Luminosity Needs · Precise knowledge of dL / dE (~ 1%) · Need to know incoming energy distribution · Want relative lumi monitor pulse-to-pulse?

Beam Instrumentation · · · · · · Beamstrahlung monitors Spot size/bunch length/deflection scans Pair monitor Radiative Bhabha Two photon monitor ?????

Detector Instrumentation · Low angle e+e- tagger · Forward tracker (e+e- acolinearity)

Eric Torrence

23/27

May 2002


Beyond ISR
1 350 GeV Machine + ISR + Beamstrahlung + 0.3% Linac

Pandora Assuming Gaussian energy spread
10
-1

10

-2

10

-3

10

-4

300

310

320

330

340

350

360

Collision Energy (GeV)

dn / dE


E Luminosity spectrum highly dynamic!
Eric Torrence 24/27 May 2002


Physics Example tt
1.00 Bare (Peskin+Strassler, m = 174.0 GeV, = 1.42 GeV, = 1) +ISR 0.75 +Beamstrahlung +Linac (tt) (pb)

0.50

0.25

0.00 335

340

345 2*Ebeam (GeV)

350

355

Simple Model (D. Cinabro June 26th) Flat tail + Gaussian core R = A dm t / dR = 40 MeV / 1% d t / dR = 100 MeV / 1% Comparable to other systematics
Eric Torrence 25/27 May 2002

tail

/A

core


Bhabha Acolinearity 0 Bhabha rates · Forward · Intermediate · Barrel (180-300 mRad) ~ 200 R (300-800 mRad) ~ 100 R (> 800 mRad) ~ 8R
s

E b / sin

0

Need rates from forward events, but not too far ... Tracking Based (silicon) · Excellent angular resolution · Backgrounds and radiation?
s

0.1 %?

Calorimeter Based (energy balance) · E / E < 1 % at 100 GeV · Need well understood acceptance/uniformity · Need segmentation (backgrounds) Detailed studies with backgrounds needed
Eric Torrence 26/27 May 2002


BI Wrap-up

General Thoughts · Many conceptual ideas · Need more concrete planning · IPBI meeting June 26th to kick this off Beam Energy · Where to put spectrometer device? · Detector requirements for radiative returns · Other clever ideas??? Polarization · Possible during collisions? · Detailed polarimeter design · Depolarization model Luminosity · · · · Very challenging problem Large overlap with machine side Impacts detector design Detailed studies needed now!

Eric Torrence

27/27

May 2002