Forward Proton Detectors at High Luminosity at the LHC

1. Forward Proton Detectors at High Luminosityat the LHC Monika Grothe U Turin & U Wisconsin QCD soft interactions, ICHEP06 28 July 2006 • Definition: “High luminosity” == luminosities at which event pile-up is significant • In the presence of pile-up, rapidity gap selection is no longer possible, diffractive events can only be selected with the help of forward proton taggers Physics motivation given in two previous talks in this session, J. Forshaw on diffractive Higgs and P.Bartalini on underlying event physics Will concentrate on the specific aspects of the FP420 R&D project Monika Grothe, Forward Proton Detectors at High Luminosities at the LHC, ICHEP06

2. shields color charge of other two gluons Vacuum quantum numbers “Double Pomeron exchange” Why detect diffractively scattered protons at the LHC at high luminosity ? Central exclusive production pp pXp: Discover a light (~120 GeV) Higgs Selection rules: central system is JPC = 0++ (to good approx) I.e. a particle produced with proton tags has known quantum numbers Excellent mass resolution (~GeV) from the protons, independent of decay products of the central system For light (~120 GeV) Higgs: Proton tagging improves S/B for SM Higgs dramatically CEP may be the discovery channel in certain regions in MSSM CP quantum numbers and CP violation in Higgs sector directly measurable from azimuthal asymmetry of the protons In addition: Rich QCD program Looking at the proton in QCD through a lens that filters out everything but the vacuum quantum numbers: measure diff PDFs, learn about parton correlations via GPDs, quantify soft multiple scattering effects via diff factorization breaking, ... In addition: Rich program of gamma-gamma mediated processes Monika Grothe, Forward Proton Detectors at High Luminosities at the LHC, ICHEP06

3. x=0.015 x=0.002 x=0 (beam) Where to put the detectors ? With nominal LHC optics: In CEP: 12 s = M2 With √s=14TeV, M=120GeV on average:  0.009  1% For slightly off-momentum protons, the LHC beam line with its magnets is essentially a spectrometer If diffractively scattered protons are bent sufficiently to leave the beam envelope, but little enough to remain within the circumference of the beam pipe, they can be detected by means of detectors inserted into the beam-pipe and approaching the beam envelope as closely as possible Monika Grothe, Forward Proton Detectors at High Luminosities at the LHC, ICHEP06

4. Where to put the detectors (II) ? CEP of Higgs: 12 s = M2 With √s=14TeV, M=120GeV on average:  0.009  1% Nominal LHC beam optics * =0.5m: Lumi 1033-1034cm-2s-1 @220m: 0.02 <  < 0.2 @420m: 0.002 <  < 0.02 Monika Grothe, Forward Proton Detectors at High Luminosities at the LHC, ICHEP06

5. The FP420 R&D project The aim of FP420 is to install high precision silicon tracking and fast timing detectors close to the beams at 420m from ATLAS and / or CMS Proposal to the LHCC in June 2005: CERN-LHCC-2005-025 “FP420: An R&D Proposal to Investigate the Feasibility of Installing Proton Tagging Detectors in the 220m Region at LHC” Signed by 29 institutes from 11 countries - more in the process of joining “The LHCC acknowledges the scientific merit of the FP420 physics program and the interest in its exploring its feasibility.” - LHCC Monika Grothe, Forward Proton Detectors at High Luminosities at the LHC, ICHEP06

6. How to integrate detectors into the cold section of the LHC 420m from the IP is in the cold section of the LHC Modify LHC Arc Termination Modules for cold-to-warm transition such that detectors can be operated at ~ room temperature Turin / Cockcroft Institute / CERN Monika Grothe, Forward Proton Detectors at High Luminosities at the LHC, ICHEP06

7. How to move detectors close to the beam Movable beam-pipe (pipelets) with detector stations attached Move detectors toward beam envelope once beam is stable Turin / Louvain / Helsinki Monika Grothe, Forward Proton Detectors at High Luminosities at the LHC, ICHEP06

8. Which technology for the detectors ? • 3D edgeless Silicon detectors: • Edgeless, i.e. distance to the beam envelope can be minimized • Radiation hard, can withstand 5 years at 1035 cm-2 s-1 • Use ATLAS pixel chip (rad hard) for readout Brunel / Stanford 3D Silicon in CERN testbeam this summer Monika Grothe, Forward Proton Detectors at High Luminosities at the LHC, ICHEP06

9. Silicon Detector Stations Manchester / Mullard Space Science Lab 2-3 detector stations with 8 layers each 7.2 mm x 24mm (7.2 x 8 mm2 sensors) Monika Grothe, Forward Proton Detectors at High Luminosities at the LHC, ICHEP06

10. What resolution does one achieve ? CEP of Higgs: Si pitch 40-50 m x and y orientation (x) ~ (y) ~15 m CMS IP ATLAS IP S/B for 120GeV Higgs -> b bbar depends critically on mass window around signal peak Glasgow / Manchester Monika Grothe, Forward Proton Detectors at High Luminosities at the LHC, ICHEP06

11. Why also fast timing detectors ? 25% of the inclusive QCD cross section at the LHC is diffractive events Average number of pile-up events overlaid to any hard scatter 7 @ 2x1033 cm-2s-1, 35 @ 1x1034 cm-2s-1 Average number of protons per PU event on either side of the IP: 0.012 @420m 0.055 @220m Example: H(120GeV)-> b bbar @ 2x1033 cm-2s-1 Coincidence of non-diffractive dijet production with  either 2 single-diffractive PU events  or one double-Pomeron exchange PU event is the most important background source Preliminary MC studies with Pythia and Exhume indicate S/BPU~O(1/100). Fast timing detectors that can determine whether the protons seen at 420m came from the same vertex as the hard scatter within better than 3mm: Would reduce S/BPU ~ O(1) For diffraction at the LHC: Fake diffractive events with protons from PU is major background source Monika Grothe, Forward Proton Detectors at High Luminosities at the LHC, ICHEP06

12. Injection of gas (~ atmospheric pressure) pump Ejection of gas Aluminium Cerenkov medium (ethane) Mirror Protons (Flat or Spherical?) ~ 15 cm ~ 5 cm Lens? (focusing) ~ 10 cm PMT Fast timing detectors Micro channel plate photo-multiplier tubes (MCP-PMT) were successfully employed in building a Cherenkov-light based Time-of-Flight detector with a time resolution of ~10ps (see NIM A 528(2004) 763) Would translate in z-vertex resolution of better than 3mm Two prototypes being worked on; both in FERMILAB test beam this summer QUARTIC (U Texas-Arlington): Cherenkov medium is fused Silica GASTOF (UC Louvain) Cherenkov medium is a gas Monika Grothe, Forward Proton Detectors at High Luminosities at the LHC, ICHEP06

13. At nominal LHC optics (*=0.5m): detectors at ~220m diffractive peak FP420 xL=P’/Pbeam= 1-x x=0.015 x=0.002 x=0 (beam) Why also detectors at ~220m from the IP ? ~220/240m region only suitable region <420m with space for detectors Acceptance: Detectors at 420m and 220m are complementary in their  coverage Detectors at 220m enhance acceptance for diffractively produced masses of high values Trigger: 420m is too far away from IP for detector signals to be used in the L1 trigger of ATLAS or CMS, i.e. needs to trigger either with the central apparatus alone or with detectors closer to the IP: H(120GeV) b bbar: 2-jet trigger: thresholds too high for any of signal events to pass 2-jet + 220m trigger: lower the jet trigger thresholds and still respect the L1 bandwidth limits Gains 10% of signal efficiency, in addition to the 10% achievable with the L1 muon trigger alone Monika Grothe, Forward Proton Detectors at High Luminosities at the LHC, ICHEP06

14. Detectors at 220m from the IP: TOTEM/CMS • TOTEM: • An approved experiment at LHC for measuring tot and elastic, uses same IP as CMS • TOTEM has RP detectors at ~220m from the CMS IP • TOTEM’s trigger and DAQ system will be integrated with those of CMS , i.e. • common data taking CMS + TOTEM possible • CMS and TOTEM are in the process of • defining a joint diffractive physics program • TOTEM/CMS low luminosity program: • Few days of special optics running with • *=90m @ 1031 cm-2s-1, better coverage • for diff events compared to *=0.5m • CMS/TOTEM high luminosity program unclear: • Want to operate 220m detectors routinely as • part of CMS data taking • Longevity of TOTEM Si detectors limited by radiation damage to O(1) fb-1 • Replacement with radiation hard detectors ? TOTEM t: 4-momentum transfer at proton vertex Monika Grothe, Forward Proton Detectors at High Luminosities at the LHC, ICHEP06

15. Detectors at 220m from the IP: ATLAS ATLAS groups Saclay, Prague, Cracow and Stony Brook consider placing detectors at ~220m away from the ATLAS IP: • Place two horizontal RP stations around 220m • Run at high luminosity with collision optics • Si detectors studied • Cerenkov counters for timing considered • extension of the ATLAS luminosity program, complementary to FP420 • Detectors of • 2x2 cm2 would • have acceptance: • up to ~0.16 • down to ~0.016 • at 20 beam 0<ξ<0.18 Monika Grothe, Forward Proton Detectors at High Luminosities at the LHC, ICHEP06

16. Summary • Measuring diffractive events at the LHC at luminosities > 1032 cm-2s-1 • requires forward proton tagging capabilities; rapidity gap selection is no longer • possible because of the presence of pile-up events • The FP420 R&D project aims at providing the appropriate means: • Rad-hard Si detectors in the cold region of the LHC at 420m • Fast timing detectors to reject fake diff events (protons from pile-up) • Ways of complementing with detectors at 220m (trigger, acceptance for high • masses) under study/discussion in both ATLAS and CMS/TOTEM • FP420 would add real discovery potential to ATLAS / CMS • FP420 R&D fully funded for next 12 months (~1000K CHF) • Technical design proposal by Feb 2007 to ATLAS and CMS • If accepted by ATLAS and/or CMS, Technical Design Report(s) could go to LHCC in spring 2007 • Detector installation could take place during first long LHC break (~2008/2009) Monika Grothe, Forward Proton Detectors at High Luminosities at the LHC, ICHEP06

17. Backup Monika Grothe, Forward Proton Detectors at High Luminosities at the LHC, ICHEP06

18. Proposal submitted to LHCC last June 58 authors 29 institutes Authors from: ATLAS, CMS, TOTEM CDF, D0, LHC • Close collaboration with • ATLAS and CMS • Contacts: • B. Cox (Manchester, ATLAS) • A. De Roeck (CERN, CMS) Monika Grothe, Forward Proton Detectors at High Luminosities at the LHC, ICHEP06

19. The physics interest of CEPMSSM: intense coupling regime • Intense-coupling regime of the MSSM: • Mh~MA ~ MH ~ O(100GeV): their coupling to, WW*, ZZ* strongly suppressed •  discovery very challenging at the LHC • Cross section of two scalar (0+) Higgs bosons • enhanced compared to SM Higgs • Production of pseudo-scalar (O-) Higgs • suppressed because of JZ selection rule • Superior missing mass resolution • from tagged protons allows to separate h, H • Spin-partity of Higgs can be determined from • the azimuthal angles between the two tagged • protons (recall JZ rule only approximate) • CEP as discovery channel 100 fb see Kaidalov et al, hep-ph/0307064, hep-ph/0311023 - 10 fb 1 fb 120 140 Monika Grothe, Forward Proton Detectors at High Luminosities at the LHC, ICHEP06

20. The physics interest of CEPMSSM: CP violation in the Higgs sector “3-way mixing” scenario of CP-violating MSSM: the 3 neutral Higgs bosons are nearly degenerate, mix strongly and have masses close to 120 GeV Superior mass resolution from tagged proton allows disentangling the Higgs bosons by measuring their production line shape Explicit CP-violation in Higgs sector manifests itself as asymmetry in the azimuthal distribution of tagged protons (interference of P- and P+ amplitudes) (Khoze et al., hep-ph/0401078)  CEP as CP and line-shape analyzer ! J. Ellis et al., hep-ph/0502251 Hadronic level cross section when Higgs bosons decay into b bbar, for different values of mixing angles 120 124 Monika Grothe, Forward Proton Detectors at High Luminosities at the LHC, ICHEP06

21. The physics interest of CEPMSSM: intense coupling regime Azimuthal angle between outgoing protons sensitive to Higgs spin-parity: JP=0+ vs JP=0- (recall JZ selection rule only approximate) 100 fb 0 - 1 fb 0 + Kaidalov et al., hep-ph/0307064 Monika Grothe, Forward Proton Detectors at High Luminosities at the LHC, ICHEP06

22. FP420 alignment • @ 1 x 1033 cm-2 s-1 expect ~ 100 - events / fill with standard trigger thresholds • Simulations indicate precision is better than necessary (theoretical limit is LHC beam energy uncertainty , 0= 0.77 GeV ~ 50 microns) Monika Grothe, Forward Proton Detectors at High Luminosities at the LHC, ICHEP06