K . Österberg High Energy Physics Division, Department of Physical Sciences, University of Helsinki & Helsinki Inst

1. Small X and Diffraction 2003 at Fermilab 17-20.9.2003 The TOTEM Experiment K. Österberg High Energy Physics Division, Department of Physical Sciences, University of Helsinki & Helsinki Institute of Physics on behalf of the TOTEM Collaboration http://totem.web.cern.ch/Totem/

2. Collaboration

3. The measurement of stot • Historical: CERN tradition (PS-ISR-SPS) • Dispersion relation (logs),   2.0 • Current model predictions: 100-130 mb (at s = 14 TeV) • Aim of TOTEM: ~1% accuracy • Using the luminosity independent method • Absolute determination of luminosity Optical Theorem:

4. To measure the total cross section with ~ 1% precision: • measure elastic rate to lowest possible t (t  10-3 GeV2) and extrapolate rate to t = 0 with a precision of < 0.5 % • measure total inelastic rate with a precision of < 1 % • Roman Pot detectors to measure leading protons - T1 and T2 detectors to measure inelastic events ~150m ~215m

5. vx(1100) vx(1540) vy(1540) vy(1100) Special LHC optics for the measurement of leading protons • Measuring elastic protons with t  10–3 GeV2  scattering angles of a few rad • At the IP : small beam divergence • [sq=(e / b*)1/2]  large b* (b* O(km)) • At the detector stations: • y = Leff,yqy* + vy y* • x = Leff,xqx*+vx x*+Dx x • Optimal conditions: • parallel to point focusing planes (v = 0)  • unique position – scattering angle relation • large Leff scattered proton at sizeable • distance from the beam center (~ 1 mm) • lowest possible beam emittance (  1 m . rad) • Luminosity :  1028 cm-2 s-1 • Two alternative optics (b*= 1100 m and 1540m) are under careful study: • - With b*= 1540 m parallel to point focusing planes in x and y simultaneously at ~220 m High * optics: lattice functions

6. b* = 1100 m Elastic scattering acceptance * = 1100 m * = 1540 m Large t (1-10 GeV2) elastic scattering will be measured using injection optics (* = 18 m)

7. Elastic rate at t = 0: statistical and systematical uncertainties L = 1028 cm-2 s-1 run time = 4 . 104 s 10 m detector position uncertainty Total systematical uncertainty < 0.5 % Systematical uncertainties: beam angular divergence and crossing angle, optical functions, beam position, detector position and resolution, pot alignment, effect of backgrounds (beam halo, double Pomeron exchange).

8. t acceptance and t resolution 50 % t acceptance vs detector position w.r.t. the beam center uncertainty on t acceptance vs uncertainty of detector position (%) t=0.004 GeV2 A=44% t=0.01 GeV2 A=67%  = 1100 m t=0.004 GeV2 A=64% t=0.01 GeV2 A=78% = 1550 m  (t)/t (1 arm) vs detector resolution • smallest possible t measured when distance between sensitive edge of detector and bottom of pot is as short as possible • detector resolution of  20 m sufficient • detector position w.r.t. the beam center should be known to better than 20 m total without beam divergence

9. CMS Hybrid ~3cm Leading proton detectors • High and stable efficiency near the edge facing the beam, edge sharpness < 10 m  try to do detectors with thinner guard rings than present LHC technology  0.5 mm • Detector size is  3  4 cm2 • Spatial resolution  20 m • Moderate radiation tolerance ( 1014 1 MeV neutron / cm2 equivalent) • Currently four different silicon based options are actively pursued: • cut planar strip detectors operated at cryogenic temperatures (“cold silicon”) • development of cut planar strip detectors (for operation at higher temperatures) • 3D-detectors with active edges • planar strip detectors with active edges

10. p+ C p+ D B A B A n+ n+ Cut edge reconstruction(2002) Cold silicon Planar strip detectors without guards rings operated at cryogenic temperatures (~ 130 K). Efficiency • low bias voltage • radiation hard Z. Li et al, "Electrical and TCT characterization of edgeless Si detector diced with different methods", IEEE NSS Proc., San Diego, Nov. 2001 Edge at: 0+20micron Development of planar technology cut edge cut edge Idea: additional n+ or p+ ring to prevent current C Goal: increase the operation temperature

11. 3D detectors with active edges Brunel, Hawaii, Stanford • CERN Courier, Vol 43, Number 1, Jan 2003 • fast charge collection • low bias voltage • radiation hard signal a.u. edge sensitivity 5-20 m position [mm] Planar strip detectors with active edges Brunel, Hawaii, Stanford TRADITIONAL PLANAR DETECTOR + DEEP ETCHED EDGE FILLED WITH POLYSILICON E-field p + Al signal a.u. n + Al position [mm] edge sensitivity 20 m n + Al

12. Design of a Roman Pot first prototype ready by end 2003 • Mechanical design of a thin window • Secondary vacuum: outgassing and RF shielding; radiation hardness • Integration of detectors inside the pot - mounting, cooling, routing • High mechanical precision ( 20 m) and reproducibility QRL (LHC Cryogenic Line) Roman Pot station design and tunnel integration 4m

13. Microstation – an option to Roman Pots • A compact and light but still a robust and reliable system • Integrated with the beam vacuum chamber • Geometry and materials compatible with machine requirements • Detector movement with m accuracy Emergency actuator Development in cooperation with LHC machine groups Inch worm motor 6cm Space for cables and cooling link Inner tube for rf fitting Detector Space for encoder Note: A secondary vacuum is an option. M. Ryynänen, R. Orava. /Helsinki group

14. Forward inelastic detectors T1 & T2 • T1: 5 planes of CSC chambers/side • coverage: 3.1 <  < 4.7 & full azimuthal • spatial resolution better than 0.5 mm • T2: 5 planes of silicon detectors/side • coverage: 5.3 <  < 6.7 & full azimuthal • spatial resolution better than 20 m IP 7.5 m 3.0 m T1 detector HF Castor  IP 13.6 m 0.4 m T2 detector

15. TOTEM+CMS+ CASTOR Measurement of the inelastic rate • T1, T2 and the forward leading proton detectors allow fully inclusive trigger: • DD, MB -- double arm inelastic trigger • SD -- single arm inelastic + single arm leading proton • Elastics, DPE -- double arm leading proton trigger • Vertex reconstruction necessary for disentangling beam-beam events from background Event loss < 2% Uncertainty < 1% Diffraction Combining TOTEM and CMS makes a large acceptance detector. 90 % of all diffractive protons detected (high ) Diffractive measurements at LHC energies important for the understanding of cosmic ray events.

16. p1 p’1 p M2=x1x2s p p2 p’2 CMS/TOTEM collaboration for high luminosity (* = 0.5 m)diffraction 150 m 215 m 308 m 420 m 338 m e.g. Double Pomeron Exchange (DPE) M (GeV) x1= x2 x=Dp/p proton momentum loss Trigger via Roman pots x > 2.5% Trigger via rapidity gap/central system x < 2.5%

17. Exclusive DPE – proton acceptance and mass resolution (* = 0.5 m) Event fraction with both protons within acceptance vs central system mass Mass resolution of central system 1 pp p + X + p 0.03 pp p + X + p all all 215 m  (mass)/mass 308 m 0.02 420 m accepted fraction 0.01 0 100 300 500 700 mass of system X (GeV) 0.5 0.04 all 308 m 420 m 0.03  (mass)/mass 0.02 0.01 0 0 140 60 100 180 60 100 140 180 mass of system X (GeV) mass of system X (GeV) At 120 GeV mass for central system: 50 % proton efficiency and 2 % resolution

18. Running scenario • Total Cross Section and Elastic Scattering • Several 1 day runs with high b* • Several 1 day runs with b* = 18 m for large-t elastic scattering • Diffraction • Runs with CMS with high b* for L =1028cm-2 s-1 • Runs with CMS with b* = 0.5 m for L < 1033cm-2 s-1 Plans • Test of silicon detectors (2003-04) • Roman pot prototype by end 2003 • Technical Design Report by end 2003 • CMS/TOTEM collaboration for high luminosity diffraction

20. Backup Slides

21. Elastic scattering Coplanarity test, background rejection: azimuthal angle resolution Detector resolution = 20 mm

22. Total TOTEM/CMS acceptance (* = 1540 m) RPs

23. log(-t) (GeV2) Elastic and total TOTEM/CMS acceptance (* = 18 m) b = 18 m b = 1540 m RPs RPs

24. Radiation fluence in the RP silicon detectors(N.Mokhov,I. Rakhno,Fermilab-Conf-03/086) Maximum fluence (1014 cm-2) for charged hadrons (E>100 KeV , L= 1033 cm-2 s-1, t=107s): RP4 (215 m)  Vertical: 0.58, Horizontal: 6.7 Dose (104 Gy/yr) RP4 (215 m)  Vertical: 0.37 (max: 1.9), Horizontal:1.2 (max:55) Main source of background: pp collisions Tails from collimators and beam-gas scattering ~ 0.1-1% Radiation level manageable

25. Forward inelastic detector T1 RAILS ARE ASSEMBLED ON A TRUSS STRUCTURE, TO WITHSTAND THE FLEXURAL LOAD THE TRUSS IS COMPLETELY RESTRAINED ON THE OUTERMOST SPACER RING PUSH/PULL RODS AT THE END TIE THE 2 TRUSSES AND LIMITS THE TORSION BASIC SOLUTION: STEEL MADE, ONE TRUSS WEIGHS ROUGHLY 120 Kg PUSH ROD: COULD BE MADE OF ALUMINIUM OR FIBERGLASS (BETTER PARTICLE TRANSPARENCY) AND/OR ARC-SHAPED PUSH/PULL RODS TRUSS (In agreement with CMS)

26. Forward inelastic detector T2 Lightweight Structure Space for services  470 mm Bellow Weight estimation: ~30 Kg Thermal Insulation 400 mm

27. Trigger and event rates Event rates at L = 1028 cm-2 s-1 : Elastic (~ 30 mb) ~ 300 Hz Inelastic (~ 80 mb)  100 Hz (suitably prescaled) Running time per high-b run ~ 2·104 s (10 hours, 50% efficiency): ~ 6 ·106 elastic events ~ 2 · 106 inelastic events • Statistics (large-t elastic) : • t ~ 0.5 GeV2 : ~ 200 evts/bin (0.02 GeV2 bins) • t ~1.5 GeV2 : ~ 80 evts/bin (0.05 GeV2 bins) b* = 18 m 2800 bunches L ~ 1032 cm-2 s-1 for 2·104 s (10 hours, 50% efficiency) • t ~ 6 GeV2 : ~ 25 evts/bin (0.1 GeV2 bins)

28. x=0.06 x=0.01 x<10-3 Diffraction at high  -t=10-2 -t=10-1 log(-t) (GeV2) 90% of all diffractive protons are seen in the Roman Pots

29. Dispersion function for LHC low * optics (CMS IR) horizontal offset x=Dx For a diffractive proton with a 5  10-3 momentum loss to give an offset in the horizontal plane of (at least) 5 mm  dispersion in x  1 m  need proton detectors located > 400 m from interaction point. Dx x y Optical function  in x andy(m) Dispersion in horizontal plane(m) CMS

30. Acceptance vs mass of central system pp p + X + p • Combined acceptance of • all locations (dotted) • 420 m + 215 m (dashed) • 215 m alone (solid) • 420 m alone (dash-dotted) • 308/338 m location brings 10-15 % more acceptance 1 fraction of events with both protons within acceptence 0 400 800 0 0 mass of system X (GeV)

31. Trigger timing of RP4 at 215 m

32. Case study: L1 trigger for diffractive Higgs based on decay products • Start from diffractive Higgs sample with auxiliary conditions • Both protons within acceptance of leading proton detectors • Both b-jets within Silicon Tracker acceptance (||<2.5) since b-tag will anyhow have to be required to reduce gg background. Use 2 most energetic jets in ||<3. diffractive Higgs characteristics: back-to-back in azimuthal, small forward ET (3<||<5) and ET sum  MH. diff. Higgs diff. Higgs forward ET (3<||<5) azimuthal angle correlation L = 1033 cm-2 s-1 MH = 120 GeV inelastic inelastic

33. Case study: L1 trigger for diffractive Higgs based on decay products Combining 2 jet azimuthal angle sum, ET sum,  sum and difference + forward ET 0 diffractive Higgs inelastic bkg -0.7 log10(efficiency) Preliminary !! MH = 120 GeV log10(Higgs efficiency) -0.8 -2 L = 1033 cm-2 s-1 -0.9 -1 -4 3 4 2 cut on combined likelihood log10(background rate(Hz)) If allowed additional L1 rate from a diffractive Higgs trigger is 250 Hz    12 % (includes L1 trigger efficiency, protons and b jets within resp. detector acceptance) In addition signal is affected by Br (H  bb), tagging efficiency of b-jets and HLT efficiency.