Interaction Regions, Backgrounds, IP Beam Instrumentation. Eric Torrence University of Oregon

Transcription

1 Interaction Regions, Backgrounds, IP Beam Instrumentation Eric Torrence University of Oregon Eric Torrence 1/27 August 2005

2 Machine Detector Interface Machine and Cost! Detector Physics Machine Detector Interface is a complicated optimization problem. Need best configuration for the physics program Example MDI topics Crossing Angle - Final Focus Layout Final Doublet L* Machine Backgrounds IP Beam Instrumentation (Energy, Polarization) Luminosity Spectrum Determination Instrumentation in Forward Region Way too much information to cover. Couldn t even attend all relevant sessions... Eric Torrence 2/27 August 2005

3 ILC Working Group 4 Beam Delivery and Interaction Region see also A. Seryi WG4 Summary August 19 th Eric Torrence 3/27 August 2005

4 From Cartoon at KEK Interaction Region Layout 1 st ILC Workshop November 2004 to Design at RHUL BDIR WS London June 2005 Full optics for all beamlines, 2 mrad and 20 mrad designs explored in detail, up/downstream instrumentation present for both IRs. Working now on refinements, evaluating performance of designs Eric Torrence 4/27 August 2005

5 20 mrad crossing angle Separate incoming and extraction beamlines More amenable to high luminosity? Cleaner downstream diagnostics? May be compatible with γγ and > 1 TeV Expect good operational margins and flexibility but Crossing Angle Comparison Reliance on crab cavity Reduced detector hermeticity Need to correct solenoid crossing (DID or other) Somewhat higher pair backgrounds 2 mrad crossing angle Lots of recent work (could still be improved?) Improves 20 mrad issues (crab, hermeticity, DID) Downstream instrumentation more difficult? More particle losses downstream, closer to IP More constrained design, problems with high Lumi Derived from A. Seryi, other opinions exist... Not at all obvious which is best in the big picture continue to develop and understand both... Eric Torrence 5/27 August 2005

6 Extraction-Line Losses From A. Seryi L 20 mrad IR vs 2 mrad IR L Nominal High Lumi Low ~ 2 W Very Low < 1 W High ~1000 W Very Low < 1 W E Nominal High Lumi preliminary & qualitative High Very High To be evaluated Low ~ 1 W Low ~ 1 W E 500 GeV 1 TeV 500 GeV 1 TeV Numbers in Watts show losses on SC FD Magnets Personal Opinion: Current high Lumi parameter sets may be unrealistic, but they probably give a good indication of where the machine wants to go... Remember: ILC Lumi = 10,000 x SLC Lumi achieving this will be a major (the major?) challenge of ILC Eric Torrence 6/27 August 2005

7 20 mrad Detector Integrated Dipole With 20 mrad crossing-angle Polarization vector is rotated (difficult for precision) Orbit bump causes synchrotron radiation - limits σ y (30% lumi) 20 mrad, no correction e + e e e Detector Integrated Dipole (DID) offers a good machine solution align field along incoming beam direction But likely causes difficulties for detector: Non-uniform solenoid field Background issues (redirecting pairs) Concepts asked to evaluate if significant impact. Tracking issues under study, LDC (Busser) indicates higher TPC backgrounds with current masking design. Significance not clear. Eric Torrence 7/27 August 2005

8 Alternate Crossing Angles Advanced design for 20 mrad final doublet Now thinking about reducing crossing angle by reducing material between coils B. Parker, BNL Angles down to mrad will be studied as alternates to baseline Likely to improve 20 mrad issues, incompatible with γγ Head-on Redux Complicated magnets and potentially large losses in 2 mrad has prompted a renewed look at head-on options: RF kicker (Y. Iwashita) and SLC-style separator (L. Keller) Needs large effort to become realistic alternative Eric Torrence 8/27 August 2005

9 Backgrounds see also T. Maruyama talk August 17 th Eric Torrence 9/27 August 2005

10 Background Sources IP Backgrounds (Good backgrounds) Disrupted primary beam - extraction line losses Beamstrahlung (BSL) photons e + e - pairs from BSL γ s pair backsplash from final doublet Hadrons from BSL or γγ Neutrons from e + e - pairs Radiative Bhabhas These scale with Luminosity: transport away, shield detectors. More reliable simulations Machine Backgrounds (Bad backgrounds) Synchrotron radiation Neutron back-shine from dump Muon production Collimator scraping Beam Gas These don t scale with Lumi: avoid near IP. Highly dependent upon assumptions Tedious to evaluate all in detail, but clearly important for detector and IR conceptual designs! Eric Torrence 10/27 August 2005

11 New LDC Pair Simulations LDC Studies (K. Busser) Investigate pair backgrounds in VXD and TPC for crossing angle options w/ realistic DID field Initial Conclusions Realistic DID field changes pair hit pattern Pairs (and junk) from incoming hole channeled into vertex detector L1 Pairs hitting LumiCal edge scatter photons to TPC Opening LumiCal reduces effect somewhat Details of fields and geometry very important... TPC Hits/BX 2 mrad 20 mrad 20 mrad + DID Adjust TPC backgrounds worse in 20 mrad + DID, but is this significant? Eric Torrence 11/27 August 2005

12 Background Tolerance Estimates Full simulations and physics studies are slow. What can be understood from rule of thumb background tolerances? W. Kozanecki (Saclay), et. al. Different tolerances: damage, pile-up, pattern recognition, physics performance Working assumption: 1% occupancy in tracking detectors. Conservative, but need realistic x10 safety factor. Example from Witold s Talk LDC Vertex occupancy vs. layer comparing DID/crossing angle (pairs) Data from K. Busser Interpretation (tolerance) by Witold ~ 173 hits mm -2 tr -1 (but: hot spots!?) Tol ( = 6 hits mm -2 / 50 µs) See talk Wed. Aug. 24 th for many more plots like this Eric Torrence 12/27 August 2005

13 General conclusions (Witold) More Background Tolerance 1% occupancy/readout window threshold useful for comparisions VXD (SiD, LDC) at or below 1%, GLD well below 1% TPC well below 1%* SiD tracker pileup appears to be 5-10 greater than stated tolerance High luminosity and low power parameters cause trouble *Warning: Correlated hits (i.e.: tracks) and hot-spots may drastically change these conclusions. True impact/tolerance can only be evaluated by detector experts with detailed studies in concept groups. Background Comments General limits useful to guide IR design, but also need the details. Each detector concept group must take ownership of their background estimations and work with WG4 to more towards realistic IR designs. Work generally started in all concepts. This is a lot of work, and adequate resources must be available in all concept groups to tackle all relevant background sources. Eric Torrence 13/27 August 2005

14 Vertex Tolerances Radius (cm) SiD 12 mm beampipe (Maruyama) Minimize R 1 Distance from IP (cm) Direct pairs kept away from VXD by solenoid field, but tolerances are often tight (few mm) May limit initial machine operations. Solenoid may not always run at nominal field. Detectors willing to sacrifice layer 1? Eric Torrence 14/27 August 2005

15 Variation with Parameter Sets Transverse Momentum vs. Theta C. Rimbault, LAL Orsay Nominal Low Q Large Y Low P High Lumi Nominal Edge High Lumi and Low Power problematic Unwise to push too hard here? Eric Torrence 15/27 August 2005

16 Beam Instrumentation and Forward Region see also K. Mönig s talk August 17 th Eric Torrence 16/27 August 2005

17 IP Instrumentation σ (, ), σ++ (, ), dl de Root(s) (GeV) s L 0 Fundamental IP Beam Instrumentation Goal Spin-dependent absolute collision energy spectrum Typical Components Beam Energy Beam Energy Width Beam Polarization Absolute Luminosity Differential Luminosity Spectrum Mixture of beam-based and physics-based measurements Eric Torrence 17/27 August 2005

18 Upstream and Downstream spectrometer and polarimeter designs now exist for both 2 mrad and 20 mrad schemes 20 mrad Extraction Line Beam Instrumentation Design 10 cm 10 meters Energy Chicane BVX9 z= m Polarimeter Chicane BVY1 z= m 25 GeV BVY2 z= m 3 mrad energy stripe Synchrotron Stripe Detector z= m BVY3 z= m QFX4 z= m 2 mrad energy Synchrotron Stripe Detector BVX1 z=59.69 m BVX2 z=61.99 m BVX4 z=70.49 m BVX3 z=68.19 m BVX6 z=75.09 m BVX5 z=72.79 m BVX7 z=81.29 m BVX8 z=83.59 m 0.75 m ra d GeV stripe Compton IP 250 GeV BPM BPM 25.1 GeV 35.7 GeV 12.0 cm 0.75 mrad c m Low Field BLEX z=64.29 m BLEX z=66.89 m BLEX BLEX z=77.39 m z=79.99 m WEX1 WEX1 z=65.59 m z=78.69 m Wiggler Ken Moffeit - LCWS 3 mrad energy stripe 2 mrad energy stripe Synchrotron Stripe Detector Shielding Cerenkov Detector Upstream probably cleaner, measures incoming beam parameters Downstream more challenging, but gives sensitivity to collision details Both needed to reach ultimate accuracy of a precision machine Complimentary systematics and control over collision uncertainties Eric Torrence 18/27 August 2005

19 Beam Instrumentation R&D RF BPM Triplets ~10 meters 100 µrad 1 mm Upstream spectrometer needs BPM resolution and stability at sub-100 nm level for several hours BPM Tests at ATF (nanobpm program) +/- 50 nm drifts Many discussions this meeting on advancing spectrometer designs. Tests starting in ESA this fall. Eric Torrence 19/27 August 2005

20 Physics Reference Reactions Bhabha acolinearity Best input for lumi spectrum shape Strong requirements on performance of forward tracking and calorimetry? θ 200 mrad θ e + e - e + e - µ + µ γ Radiative Returns Potentially best measure of s correct for any collision bias Actually used at LEPII serious detector systematics Also t-channel WW for polarization monitoring Stringent detector requirements δθ 0.1 Need precise tracking to ~150 mrad % per event ( limit), absolute angle known to 10-4 Γ Z Forward tracking system must be given same care and effort as precision luminosity measurements. See K. Mönig LDC talk Will likely determine ultimate precision on masses due to δ s! Need to do a good job here to reach δm ~ 50 MeV Eric Torrence 20/27 August 2005 γ θ 1 e + e - µµγ θ 2

21 Putting it all Together Root(s) (GeV) s θ γ θ 1 Ε 1 Ε 2 e + e - e + e - e + e - ΖΖ e + e - µµγ θ 2 e + e - e + e - Need combined analysis putting together all pieces and extracting physics result S. Boogert working on efficient MC generation from beam-beam simulations Goal: close the loop and show required precision can be achieved Eric Torrence 21/27 August 2005

22 Forward Detectors LDC Forward design (2 mrad, L* = 4.05 m) Luminosity Monitor ~ mrad - Outside pair backgrounds Also shields pair backsplash from lower angles Pair Monitor ~ 5-20 mrad - Front surface, machine diagnostics γγ Tagger ~ 5-20 mrad - Cal. to veto γγ electrons as SUSY background Could be all one, or several different detectors Eric Torrence 22/27 August 2005

23 Precision Luminosity Series of talks on precision luminosity - W. Lohmann et. al. Ambitious goal of 10-4 (below 10-3 probably OK) Extensive studies made for head-on Rad-hard detectors considered Initial studies for 20 mrad indicate larger backgrounds - need increased inner radius. Detailed evaluation of 20 mrad boost on detector geometry needed Ultimate OPAL precision based on phi symmetry - D. Strom May be much more difficult in crossing angle Eric Torrence 23/27 August 2005

24 Far-Forward γγ Tagging Electron hermeticity key for SUSY and other analyses Challenge: Separate 250 GeV electron from 10s TeV pair backgrounds per crossing Backgrounds to stau analysis Zhang (Orsay) Several studies done on performance for µ µ and τ τ Rely on huge suppression of γγ background ε ~ 99.9% probably required! Modest acceptance hole is OK if you know where it is - reduced efficiency 1 fb Larger hole leads to Bhabha backgrounds (1 Bhabha per 2 BX) Pair background rates problematic Eric Torrence 24/27 August 2005

25 Forward Pair Distributions Pair Energy in BeamCal (L* = 4m, B = 4T) - P. Bambade - Orsay 2 mrad Nominal 2 mrad Low Q 2 mrad High Lumi Larger energy deposition at larger angles impacts ultra-efficient electron ID 20 mrad + DID Nominal 2 mrad qualitatively better Can quantify 2 mrad - 20 mrad difference under certain assumptions/models e.g.: Factor of 1.8 in M ( τ x 0 ) reach - Bambade Differences from machine parameter sets very significant Low Q (or similar) would be most beneficial if physics demanded Hard to judge how much weight this carries in global optimization Eric Torrence 25/27 August 2005

26 MDI Structure There is no MDI working group! More of an avenue of communication between the accelerator, detector, and physics groups Most closely tied to ILC WG4 - IR layout issues + community on detector/physics side Global issues (e.g.: 1 or 2 IRs, parameters) also important WWS Interim MDI Panel - through Snowmass M. Woods, P. Bambade, T. Tauchi Needs to be expanded/reformulated to include concept representatives, WG4, and guidance from GDE MDI Communication Examples Urgent MDI questions for concepts - necessary to complete conceptual design Vertex session Tuesday with questions for WG4 Communication goes both ways... Eric Torrence 26/27 August 2005

27 Summary Wide range of topics covered at Snowmass under WG4, MDI, and IP Beam Instrumentation Key features of IR conceptual design in place Baseline crossing angles: 2 mrad and 20 mrad Intermediate mrad to be pursued as alternate Detector backgrounds depend on details of detector technology and IR geometry Large effort from concepts needed here! Beam instrumentation design proceeding Detailed evaluation of performance starting Physics reference processes also needed Stringent detector requirements, part of benchmarks Studies of forward detector performance continuing Working towards ever better understanding of MDI optimization process Eric Torrence 27/27 August 2005