Aug 13, 2005 - lumi-spectrum measurements. ⢠Energy spread at end of linac. Continuous relative monitor of core energy width. Conventional wisdom is âwire ...
Energy and Luminosity Spectrum
Eric Torrence University of Oregon Input from S. Boogert and M. Hildreth
Eric Torrence
1/13
August 2005
Outline
• MDI Questions • Upstream RF-BPM Spectrometer • Downstream SR Spectrometer • Additional Machine Diagnostics • Physics Reference Reactions • Putting it all Together • Work Plan
Focus on CDR issues and critical work for detector concept groups
Apologies for the text-heavy nature of this talk...
Eric Torrence
2/13
August 2005
Brief Introduction 0.09
σ ( −, − ), σ ( +, + ), …
0.08 0.07 0.06
dL ------dE
0.05 0.04
L0
0.03 0.02 0.01 0
490
492
494
496
498
500
502 504 Root(s) (GeV)
〈 s〉 Fundamental Goal Spin-dependent absolute collision energy spectrum Typical Components • Beam Energy • Beam Energy Width • Beam Polarization • Absolute Luminosity • Differential Luminosity Spectrum All are intrinsically related in fundamental goal Eric Torrence
3/13
August 2005
MDI Questions 14. Do you anticipate a need for both upstream and downstream polarimetry and spectrometry? What should be their precision, and what will the effect of 2 or 20 mr crossing angle be upon their performance.
SiD Reply: Both Long reply (M. Woods) stressing redundancy and complimentary systematics for both. GLD Reply: Both Short reply, similar sentiment. Also highlighted difficulty of downstream measurements. LDC Reply: Should be answered in common amongst all concepts. The ball is in our court here. Pressure will be to reduce costs. Far too early to give up on both upstream and downstream. Need to assess performance in 2 mRad and 20 mRad Eric Torrence
4/13
August 2005
Upstream Spectrometer 100 µRad
RF BPMs
1 mm
~10 meters • Bends ~ 100 µRad, lengths 10 m, 1 mm bump • Need 100 nm (or better) resolution and accuracy • Move BPMs to the beam (keep same relative position) • Calibrate alignment by ramping chicane (bipolar best) Concept, Layout, and Design Many details to be refined, but basic concept is probably good enough for CDR Operational Strategy • What is the operational strategy? What kind of ramps and how often? • What limits luminosity during ramps? Can machine auto-correct? • Ramp strategy must be consistent with precision field maps! Real thought needed here Needs to be decided for CDR (in my opinion) Need space for extra correctors? Optics problems? Eric Torrence
5/13
August 2005
Upstream Spectrometer Issues Inspired by M. Hildreth email BPM Issues • nBPM gives 20-30 nm, but aperture too small • Mechanical stability over length limits to ~100 nm? • Need dedicated spectrometer BPM design (one plane only? rectangular designs?) • Is 1000:1 range:precision rule of thumb absolute? • Is this really just an electronics issue? Work has already started, but more spectrometer-specific BPM efforts necessary.
Magnet Issues • Magnet technology (warm steel vs. SC) • Field mapping and in-situ instrumentation • End-fields dominate ∫ B dl uncertainty Not necessarily CDR issues, but need serious work
Eric Torrence
6/13
August 2005
Downstream Spectrometry Polarimeter Chicane
Ken Moffeit - June
Energy Chicane
2 mrad extraction line
BHEX3A z=190.06 m x=-- cm
BYCHIC z=~198 m x=-- cm
BYCHICM z~208 m x=-- cm
Focus z~214 m
BHEX3B z=192.36 m x=-- cm
2 mRad Extraction Line
BYCHICM z~218 m x=----- cm
2rd
Synchrotron
BHEX3C z=194.66 m x=-- cm
20 x 50 cm
Plan View
BYCHIC z~228 m x=----- cm
Angle 10.563 mrad
Stripe Detector Beam Stay Clear +- 10 cm
BYCHIC z=174.4 m x=----- cm
Angle 2.0 mrad
Angle 8.850 mrad Angle 7.138 mrad
Angle 3.621 mrad
Angle 5.425 mrad Angle 3.712 mrad
Angle 5.242 mrad BYCHIE z~ 131.0 m x= cm
10 cm
BYCHIE z~151.0 m x= cm
BYCHIE z=154.4 m x=----- cm
Compton IP
10 m BHEX4C z=m x= cm
BHEX2 z=129.060 m x=71.25 cm SEXF2 z=116.66 m x=63.98 cm
QEXF4 z=112.460 m x=61.52 cm
BYCHIC z=106.46 m x=58.00 cm
BYCHICM z=82.360 m x=43.87 cm
QEXF5 z=123.060 m x=67.73 cm
Angle 6.863 mrad
QEXF4B z=118.860 m x=65.27 cm
SR Detectors
BHEX4B z= m x= cm
BHEX4D z= m x= cm
BHEX4A z=~232 m x= cm
BHEX4E z= m x= cm
BYCHICM z=84.460 m x=45.10 cm
BYCHIC z=60.364 m x=30.973 cm
SEXF1 z=28.861 m x=12.51 cm QEXF1 z=26.161 m x=10.92 cm
Angle 5.863 mrad
QEXF1B z=31.061 m x=13.79 cm
Beam Stay Clear +- 10 cm
20 cm Photon Beamstrahlung Cone +- 1 mrad
Y
Angle 2.0 mrad at IR
1 mRad Cone Wigglers
2nd Focus 214 meters
8 meters
Synchrotron
Sextupole Quad Quad Quad
Cerenkov
Stripe Detector
Detector
Beam Stay Clear 10cm
10 cm
Side View
Compton IP
5 cm 0
Angle -3 mrad
Angle 3 mrad
Angle -3 mrad
Angle 3 mrad
-5 cm -10 cm
Dispersion = 66 cm 250 GeV
Beam Stay Clear 10cm
Angle 2 mrad
25.1 GeV 35 GeV
Dispersion = 20 mm 250 GeV
Wiggler Low Field
Energy Slit Eric Torrence
C Detector
Dispersion = 66mm 250 GeV
Vacuum Chamber
25 GeV
25 GeV
12 .3 cm
17.8 cm
Synchrotron
Stripe Detector
3 mRad 25 GeV
2 mRad SR Detectors
K Moffeit 20 Apr 05
7/13
August 2005
Downstream Spectrometer Design What is done • Basic concept and detector strategy • Sketch of 2 mRad and 20 mRad extraction geometry to accommodate spectrometer and polarimeter What is not done • Feasibility of components - large apertures, shielding e.g.: wiggler is not at all “standard” or “trivial” • Simulation of beam transport including realistic tracking, stray doublet fields, solenoid, DID, etc. Key Work • Get IP to dump simulation working with BDSIM, gradually include more realistic features. • Specify/design realistic elements, esp. wiggler • Assess 2 mRad and 20 mRad performance including background estimates, shielding, stayclear tolerances, etc. Interested parties welcome here... Eric Torrence
8/13
August 2005
Machine Diagnostics Need to have specifications in CDR for additional machine instrumentation useful for energy and lumi-spectrum measurements
• Energy spread at end of linac Continuous relative monitor of core energy width. Conventional wisdom is “wire scanner” at chicane. Where does the fit in the instrumentation section? What is the expected performance?
• Energy vs. z bunch profile This would be tremendously useful for monitoring linac wakefield effects, key part of collision biases. Does this really work at the ILC, where does it fit, can it be used as more than an MD diagnostic?
Input from machine instrumentation people needed... Eric Torrence
9/13
August 2005
Physics Reference Channels Bhabha acolinearity ∆θ
• Best input for lumi spectrum shape • Strong requirements on performance of forward tracking and calorimetry? θ ∼ 200 mRad • Reasonably well studied analysis
e+e- Õe+e-
µ + µ − γ “Radiative Returns”
cos Θ
• Potentially best measure of 〈 s〉 correct for any collision bias • Only possibility for WW threshold? • Actually used at LEPII serious detector systematics
γ e+e- Õ µµγ
θ1 θ2
Need precise tracking to ~100 mRad
1 0.9
δΘ ≈ 0.1 % per event ( Γ Z limit)
0.8
θ1 = θ2
0.7
Absolute angle known to 10-4
0.6 0.5 200
300
400
500 600
800 1000
Not a CDR issue for machine, but directly impacts detector concepts
Collision Energy (GeV)
Eric Torrence
10/13
August 2005
Other Reference Channels ZZ → qqll • Useful as cross check of 〈 s〉 • Lower statistics, but less detector systematics than Zγ • Only briefly considered (that I am aware of) • Ultimate resolution/accuraccy unknown...
e+e- Õ ΖΖ
Bhabha/Mu-pairs direct energy/momentum • Could potentially cross-check drifts in 〈 s〉 • Limited by detector calibration and resolution • Already envisioned for detector calibration?
Ε1
Ε2 e+e- Õe+e-
Also related: t-channel WW for polarization Need more detector effort on forward tracking, esp. systematics. Forward tracking needs as much care as lumi monitor... Possibility to design specific calorimeter rings to improve performance? Physics benchmarks do include Bhabhas and µµγ need to raise awareness of importance in some detector groups Eric Torrence
11/13
August 2005
Putting it all Together Need to demonstrate that lumi spectrum can be extracted from available inputs and fed back into physics analysis Generation Layer Simulation Layer Analysis Layer Machine Parameters GuineaPig Physics Generator
beam params
dL/dE Extraction
output beams four-vectors
Physics
Partly technical check of parameterization and technique, partly demonstration that there aren’t loopholes in logic. Exploit G. White’s work on IP feedback simulations Integrate into ILC generators for easy use by physics groups. S. Boogert - working on extracting machine parameters from Glen’s files into convenient format for generators...
Eric Torrence
12/13
August 2005
Possible Snowmass Work BPM performance and operational strategy D. Miller, M. Hildreth, M. Ross?
IP -> Dump Simulations E. Torrence w/ help from BDSIM experts (i.e.: Carter)
Statement on Machine Diagnostics M. Ross, G. Blair?
Highlight Reference Physics Reactions to Concepts T. Barklow, others? Worth preparing a short talk on this for concepts?
Full Lumi Spectrum extraction and application S. Boogert Eric Torrence
13/13
August 2005
