Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC K. Österberg High Energy Physics Division, Department of Physical Sciences, University of Helsinki & Helsinki Institute of Physics on behalf of the TOTEM Collaboration The TOTEM Experiment Small X and Diffraction 2003 at Fermilab

Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC Università di Bari and Sezione INFNUniversità di Bari and Sezione INFN, Bari, Italy Institut für Luft- und Kältetechnik,Institut für Luft- und Kältetechnik, Dresden, Germany CERN,CERN, Geneva, Switzerland Università di Genova and Sezione INFNUniversità di Genova and Sezione INFN, Genova, Italy Institut des Sciences Nucléaires, IN2P3/CNRSInstitut des Sciences Nucléaires, IN2P3/CNRS, Grenoble, France University of Helsinki and Helsinki Institute of Physics, Helsinki, Finland Warsaw University of Technology, Plock, Poland Academy of Sciences, Praha, Czech Republic Brunel University, Uxbridge, UK Collaboration

Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC Optical Theorem: Historical: CERN tradition (PS-ISR-SPS) Dispersion relation (logs) ,   2.0 Current model predictions: mb (at  s = 14 TeV) Aim of TOTEM: ~1% accuracy Using the luminosity independent method Absolute determination of luminosity The measurement of  tot

Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC ~150m ~215m To measure the total cross section with ~ 1% precision: measure elastic rate to lowest possible t (t  GeV 2 ) 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

Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC Special LHC optics for the measurement of leading protons v x (1100) v y (1100) v y (1540) v x (1540) High  * optics: lattice functions Measuring elastic protons with t  10 –3 GeV 2  scattering angles of a few  rad At the IP : small beam divergence [       ]   large  * (  *  O(km))  At the detector stations: y = L eff,y  y * + v y y * x = L eff,x  x * + v x x * + D x  Optimal conditions: parallel to point focusing planes (v = 0)  unique position – scattering angle relation large L eff  scattered proton at sizeable distance from the beam center (~ 1 mm) lowest possible beam emittance (   1  m. rad) Luminosity :  cm -2 s -1 Two alternative optics (  * = 1100 m and 1540 m) are under careful study: - With  * = 1540 m parallel to point focusing planes in x and y simultaneously at ~220 m

Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC  * = 1100 m Elastic scattering  * = 1540 m acceptance Large t (  1-10 GeV 2 ) elastic scattering will be measured using injection optics (  * = 18 m)  * = 1100 m

Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC Elastic rate at t = 0: statistical and systematical uncertainties L = cm -2 s -1 run time = 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).

Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC (%) t acceptance and t resolution t=0.004 GeV 2 A=64% t=0.01 GeV 2 A=78% t=0.004 GeV 2 A=44% t=0.01 GeV 2 A=67%  = 1100 m  = 1550 m 50 % t acceptance vs detector position w.r.t. the beam center uncertainty on t acceptance vs uncertainty of detector position total without beam divergence  (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 Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC ~3cm CMS Hybrid 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 cm 2 Spatial resolution  20  m Moderate radiation tolerance (  MeV neutron / cm 2 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

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

Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC  CERN Courier, Vol 43, Number 1, Jan D detectors with active edges Brunel, Hawaii, Stanford edge sensitivity  5-20  m fast charge collection low bias voltage radiation hard Planar strip detectors with active edges Brunel, Hawaii, Stanford TRADITIONAL PLANAR DETECTOR + DEEP ETCHED EDGE FILLED WITH POLYSILICON edge sensitivity  20  m n + Al p + Al E-field signal a.u. position [  m] signal a.u. position [  m]

Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC Design of a Roman Pot 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 4m QRL (LHC Cryogenic Line) first prototype ready by end 2003 Roman Pot station design and tunnel integration

Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC Inner tube for rf fitting Inch worm motor Emergency actuator Detector Space for cables and cooling link Space for encoder 6cm Note: A secondary vacuum is an option. M. Ryynänen, R. Orava. /Helsinki group 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 Microstation – an option to Roman Pots Development in cooperation with LHC machine groups

Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC Forward inelastic detectors T1 & T2 T1 detector T2: 5 planes of silicon detectors/side coverage: 5.3 <  < 6.7 & full azimuthal spatial resolution better than 20  m 0.4 m 13.6 m T1: 5 planes of CSC chambers/side coverage: 3.1 <  < 4.7 & full azimuthal spatial resolution better than 0.5 mm T2 detector 3.0 m 7.5 m HF Castor  IP IP

Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC 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% Measurement of the inelastic rate TOTEM+CMS+ CASTOR 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.

Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC  =  p/p proton momentum loss Trigger via Roman pots  > 2.5 % Trigger via rapidity gap/central system  < 2.5 % e.g. Double Pomeron Exchange (DPE) p1p1 p2p2 p’2p’2 p’1p’1 M2=sM2=s p p M (GeV)   =  2 CMS/TOTEM collaboration for high luminosity (  * = 0.5 m) diffraction 420 m 308 m215 m 150 m 338 m

Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC Exclusive DPE – proton acceptance and mass resolution (  * = 0.5 m) 0 At 120 GeV mass for central system:  50 % proton efficiency and  2 % resolution mass of system X (GeV) accepted fraction pp  p + X + p 1 Event fraction with both protons within acceptance vs central system mass all 308 m 420 m Mass resolution of central system pp  p + X + p 215 m all  (mass)/mass mass of system X (GeV) mass of system X (GeV)  (mass)/mass all 308 m 420 m

Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC Running scenario Total Cross Section and Elastic Scattering 1.Several 1 day runs with high  * 2.Several 1 day runs with  * = 18 m for large-t elastic scattering Diffraction 1.Runs with CMS with high  * for L =10 28 cm -2 s -1 2.Runs with CMS with  * = 0.5 m for L < cm -2 s -1 Plans Test of silicon detectors ( ) Roman pot prototype by end 2003 Technical Design Report by end 2003 CMS/TOTEM collaboration for high luminosity diffraction

Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC

Backup Slides

Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC Coplanarity test, background rejection: azimuthal angle resolution Detector resolution = 20  m Elastic scattering

Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC Total TOTEM/CMS acceptance (  * = 1540 m) RPs

Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC t) (GeV 2 ) log(-t) (GeV 2 )  m  m Elastic and total TOTEM/CMS acceptance (  * = 18 m) RPs

Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC (N.Mokhov,I. Rakhno,Fermilab-Conf-03/086) Radiation fluence in the RP silicon detectors (N.Mokhov,I. Rakhno,Fermilab-Conf-03/086) Maximum fluence (10 14 cm -2 ) for charged hadrons Maximum fluence (10 14 cm -2 ) for charged hadrons (E>100 KeV, L= cm -2 s -1, t=10 7 s): (E>100 KeV, L= cm -2 s -1, t=10 7 s): RP4 (215 m)  Vertical: 0.58, Horizontal: 6.7 Dose (10 4 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

Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC 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) Forward inelastic detector T1

Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC Bellow Thermal Insulation Lightweight Structure Space for services 400 mm  470 mm Weight estimation: ~30 Kg Forward inelastic detector T2

Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC Event rates at L = cm -2 s -1 : Elastic (~ 30 mb)~ 300 Hz Inelastic (~ 80 mb)  100 Hz (suitably prescaled) Running time per high-   run ~ 2·10 4 s (10 hours, 50% efficiency): ~ 6 ·10 6 elastic events ~ 2 · 10 6 inelastic events Statistics (large-t elastic) : -t ~ 0.5 GeV 2 :~ 200 evts/bin(0.02 GeV 2 bins) -t ~1.5 GeV 2 :~ 80 evts/bin(0.05 GeV 2 bins)  * = 18 m 2800 bunches L ~ cm -2 s -1 for 2·10 4 s (10 hours, 50% efficiency) -t ~ 6 GeV 2 :~ 25 evts/bin(0.1 GeV 2 bins) Trigger and event rates

Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC t) (GeV 2 ) log(-t) (GeV 2 ) -t= t=10 -2     90% of all diffractive protons are seen in the Roman Pots Diffraction at high  

Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC Dispersion function for LHC low  * optics (CMS IR) CMS Dispersion in horizontal plane (m) xx Optical function  in x and y (m) For a diffractive proton with a 5  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. yy DxDx horizontal offset  x=  D x

Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC Combined acceptance of all locations (dotted) 420 m m (dashed) 215 m alone (solid) 420 m alone (dash-dotted)  308/338 m location brings % more acceptance 0 mass of system X (GeV) fraction of events with both protons within acceptence pp  p + X + p Acceptance vs mass of central system

Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC Trigger timing of RP4 at 215 m

Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC 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 E T (3<|  |<5) and E T sum  M H. azimuthal angle correlation forward E T forward E T (3<|  |<5) diff. Higgs inelastic diff. Higgs M H = 120 GeV inelastic L = cm -2 s -1

Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC Case study: L1 trigger for diffractive Higgs based on decay products inelastic bkg diffractive Higgs M H = 120 GeV L = cm -2 s -1 Combining 2 jet azimuthal angle sum, E T sum,  sum and difference + forward E T log 10 (efficiency) log 10 (Higgs efficiency) log 10 (background rate(Hz)) cut on combined likelihood 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. Preliminary !!