TOTEM early measurements Fabrizio Ferro – INFN Genova On behalf of TOTEM Collaboration INFN Sezione di Bari & Politecnico di Bari, Bari, Italy MTA KFKI RMKI, Budapest, Hungary Case Western Reserve University, Cleveland, Ohio, USA CERN, Geneva, Switzerland Università di Genova & Sezione INFN, Genova, Italy University of Helsinki & HIP, Helsinki, Finland Penn State University, University Park, USA Academy of Sciences, Praha, Czech Republic Università di Siena & Sezione INFN-Pisa, Italy Estonian Academy of Sciences, Tallinn, Estonia MPI@LHC 2008 Fabrizio Ferro – INFN Genova

Fabrizio Ferro – INFN Genova Experimental area Leading protons detected at -220m & -147m from IP LHC - IP5 CMS TOTEM Leading protons detected at 147m and 220m from IP. CMS coverage extended by TOTEM T1 and T2 telescopes Leading protons detected at +220m & +147m from IP MPI@LHC 2008 Fabrizio Ferro – INFN Genova

Fabrizio Ferro – INFN Genova Physics program Total pp cross section Elastic pp scattering in a wide t range 103 < -t < 10 GeV2 (-t~p2q2) Soft diffraction Charged multiplicity measurement in a wide  range Study of low-xBj dynamics Hard diffraction (single, central and with jet, W and heavy flavour production) Exclusive particle production in central diffraction (DPE: Double Pomeron Exchange)  and p physics Charged particle flow TOTEM CMS TOTEM Energy flow  with CMS MPI@LHC 2008 Fabrizio Ferro – INFN Genova

Fabrizio Ferro – INFN Genova Total pp cross section Possible TOTEM measurement Final goal: ~1 % accuracy Early goal: ~5 % accuracy Luminosity independent method: measurement of elastic and inelastic rate - Fundamental ingredient in any cross section measurement COMPETE collaboration Fit from available data: COMPETE Collaboration, PRL 89 (2002) 201801. MPI@LHC 2008 Fabrizio Ferro – INFN Genova

Fabrizio Ferro – INFN Genova Experimental setup Inelastic telescopes: Tracking of charged particles & vertex reconstruction in inelastic events (main goal: measurement of Ninel) T1: 3.1 <  < 4.7 T2: 5.3 <  < 6.5 T1: 18 – 90 mrad T2: 3 – 10 mrad IP5 ~ 10 m T1 HF (CMS) T2 CASTOR (CMS) ~ 14 m Roman Pots: measurement of elastic and diffractive protons near the outgoing beam Scattering angles: 5 – 500 rad (depending on beam optics) IP5 RP147 RP220 MPI@LHC 2008 Fabrizio Ferro – INFN Genova

Fabrizio Ferro – INFN Genova T1 telescope Cathode Strip Chambers(CSC) 3.1 < |h| < 4.7 5 planes: measurement of 3 coordinates per plane Primary vertex reconstruction to discriminate background (not beam-beam events) for the measurement of Ninel Vertex resolution:  ~ 2 cm, z ~ 20 cm Trigger with anodic wires () ~ 0.02  0.2 (depending on particle momentum) Multiplicity measurement CSC 3m Spatial resolution ~1mm MPI@LHC 2008 Fabrizio Ferro – INFN Genova

Fabrizio Ferro – INFN Genova T1: preparing for installation Support rails Storage and cosmic tests Status: preparing to install in 2009 ¼ ofT1 MPI@LHC 2008 Fabrizio Ferro – INFN Genova

Fabrizio Ferro – INFN Genova T2 telescope 3-GEM (Gas Electron Multiplier) 5.3 < |h| < 6.5 10 semi-planes which provide 2 coordinates on both beampipe sides Primary vertex reconstruction Trigger with pads () ~ 0.04 – 0.1 Multiplicity measurement 65(j) x 24(h) = 1560 pads Pads: Dh x Dj = 0.06 x 0.015p 2x2 mm2 __ 7x7 mm2 Strips: 256 (width/pitch: 80/400 mm) Radial resolution: ~ 100 m Azimuthal resolution: ~ 1° MPI@LHC 2008 Fabrizio Ferro – INFN Genova

Fabrizio Ferro – INFN Genova T2 installation Test Beam T2 and the beampipe CMS T2 Status: ¼ of T2 installed. Complete installation in 2009 MPI@LHC 2008 Fabrizio Ferro – INFN Genova

Fabrizio Ferro – INFN Genova Roman Pots BPM fixed to RP structure  beam position Horizontal Pot Vertical Pots BPM RP station: 2 units, 4 m distance 1 unit: 2 vertical pots / 1 horizontal and 1 BPM MPI@LHC 2008 Fabrizio Ferro – INFN Genova

Fabrizio Ferro – INFN Genova RP installed at 147 m and 220 m on both sides of IP5 MPI@LHC 2008 Fabrizio Ferro – INFN Genova

Fabrizio Ferro – INFN Genova MPI@LHC 2008 Fabrizio Ferro – INFN Genova

Fabrizio Ferro – INFN Genova Roman Pot and Proton Detectors 10 planes of Si detectors 512 strips at  45° Pitch: 66 m Resolution: ~ 20 m Detector overlap Ferrite Status: detectors installed in horizontal RPs at 220m. Complete 220m in 2009 and 147m just after. RP vertical RP horizontal RP vertical MPI@LHC 2008 Fabrizio Ferro – INFN Genova

Planar technology + CTS (Current Terminating Structure) Si CTS edgeless detectors Proton detection down to 10beam, + d (beam, = 80  600 m) To minimize d : detectors with highly reduced inactive edge (”edgeless”) Planar technology + CTS (Current Terminating Structure) I2 I1 + - biasing ring Al p+ n+ cut edge current terminating ring SiO2 n-type bulk 50µm Micro-strip Si detectors designed to reduce the inefficiency at the edge. Inefficient edge ~ 50 m 50 µm MPI@LHC 2008 Fabrizio Ferro – INFN Genova

Optics and Beam Parameters (standard step in LHC start-up) = 90 m (early TOTEM optics) = 1540 m (final TOTEM optics) Crossing angle 0.0 N of bunches 156 43 N of part./bunch (4 – 9) x 1010 3 x 1010 Emittance n [m ∙ rad] 3.75 1 10 y beam width at RP220 [mm] ~ 3 6.25 0.8 Luminosity [cm-2 s-1] (2 – 11) x 1031 (5 – 25) x 1029 1.6 x 1028 * = 90 m ideal for early running: fits well into the LHC start-up running scenario; uses standard injection (b* = 11m)  easier to commission than 1540 m optics wide beam  ideal for training the RP operation (less sensitive to alignment) * = 90 m optics optimized both for stot and diffraction. MPI@LHC 2008 Fabrizio Ferro – INFN Genova

Fabrizio Ferro – INFN Genova TOTEM physics and LHC optics Feasible physics depends on running scenarios: luminosity beam optics (β*) acceptance of proton detectors precision in the measurement of scattering angle (beam divergency ) stot(~1%), low t elastic, stot(~5%), low t elastic, high t elastic, soft diffraction (semi)-hard diffraction hard diffraction cross section luminosity EARLY  mb b nb * (m) 1540 90 2 0.5 L (cm2 s1) 1028 1030 1031 1033 TOTEM runs Standard runs MPI@LHC 2008 Fabrizio Ferro – INFN Genova

Proton detected using: Proton detection strategy Hit distribution in the RP at 220m (diffractive scattering) low *: 0.5  2 m high *: 90 y(mm) y(mm) y ~ yscatt ~ | ty | x ~   p/p 10 10 x(mm) x(mm) Proton detected using: momentum loss (low *) or transverse momentum (high *) MPI@LHC 2008 Fabrizio Ferro – INFN Genova

Fabrizio Ferro – INFN Genova Proton Acceptance > 10 % acceptance for RP 220 m DPE Measurement of cross sections for different processes (Elastic, SD, DPE, …) Study of corresponding rapidity gaps and their suppression MPI@LHC 2008 Fabrizio Ferro – INFN Genova

Fabrizio Ferro – INFN Genova Elastic scattering b*=90m L=3x1030 b*=2m L=1032 2x109 - 2.3x107 - 4000 1.2x105 500 4x104 b* = 90 m 30 3000 b* = 11 m 1 160 b* = 2 m 0.3 50 N events/day MPI@LHC 2008 Fabrizio Ferro – INFN Genova

Elastic scattering at low |t| Exponential slope B(t) b* = 1540 m b* = 90 m fit interval b* = 1540 m: |t|min = 0.002 GeV2 b* = 90 m: |t|min = 0.04 GeV2 best parameterization: B(t) = B0 + B1 t + B2 t2 MPI@LHC 2008 Fabrizio Ferro – INFN Genova

Extrapolation to the Optical Point (t = 0) at b* = 90 m (extrapol. - model) / model in d/dt |t=0 Statistical extrapolation uncertainty ∫ L dt = 2 nb-1 (5 hours @ 1029 cm-2 s-1) Common bias due to beam divergence : – 2 % (angular spread flattens dN/dt distribution) Spread between most of the models: ±1% Systematic error due to uncertainty of optical functions: ± 3% Different parameterizations for extrapolation tested (e.g. const. B, linear continuation of B(t)): negligible impact MPI@LHC 2008 Fabrizio Ferro – INFN Genova

Fabrizio Ferro – INFN Genova Trigger schemes p T1/T2 RP CMS Elastic Trigger Single Diffractive Trigger Double Diffractive Trigger Central Diffractive Trigger (Double Pomeron Exchange DPE) Non-diffractive Inelastic Trigger p Big uncertainties on expected individual cross sections p p MPI@LHC 2008 Fabrizio Ferro – INFN Genova

Measurement of the inelastic rate Inelastic double arm trigger: robust against background, inefficient at small M Inelastic single arm trigger: suffers from beam-gas + halo background, best efficiency Inelastic triggers and proton (SD, DPE): cleanest trigger, proton inefficiency to be extrapolated Trigger on non-colliding bunches to determine beam-gas + halo rates. Vertex reconstruction with T1, T2 to suppress background Extrapolation of diffractive cross-section to large 1/M2 assuming ds/dM2 ~ 1/M2 : - dsSD/dM can be measured with high b optics, not with low b (only for very high M) Acceptance single diffraction simulated extrapolated detected Loss at low diffractive masses M s [mb] trigger loss [mb] systematic error after extrapolations [mb] Non-diffractive inelastic 58 0.06 Single diffractive 14 3 0.6 Double diffractive 7 0.3 0.1 Double Pomeron 1 0.2 0.02 Total 80 3.6 0.8 MPI@LHC 2008 Fabrizio Ferro – INFN Genova

Fabrizio Ferro – INFN Genova tot measurement * = 90 m / * = 1540 m Early Later (asap) Extrapolation of the elatic cross section to t = 0: ± 4 % /  0.2 % Total elastic rate: ± 2 % /  0.1 % Total inelastic rate: ± 1 % /  0.8 % (error dominated by the loss of single and double diffractive events) Contribution from (1+2) using the systematic error from COMPETE d/ = 33% ± 1.2 % => Total error on tot (taking into account correlations): ± 5 % /  (12) % Error on luminosity (~ squared total rate) : ± 7 % /  2 % A precise measurement with * = 1540 m needs: Better knowledge of the optical functions RP alignment precision < 50 m MPI@LHC 2008 Fabrizio Ferro – INFN Genova

Very first measurements with low b* optics Using horizontal RPs dSD/dM (SD events with high mass) 0.02 <  < 0.18  2 < M < 6 TeV (M)/M = 24 % dDPE/dM 250 < M < 2500 GeV (M)/M = 2.13.5 % Using vertical RPs: high t elastic scattering dElastic/dt 2 < |t| < 10 GeV2 (t)  0.25|t|  p p SD MX2 =  s Rapidity Gap -ln    p X 2 p p2 1 p p1 DPE  Rapidity Gap -ln 1 Rapidity Gap -ln 2 p1 X p2 MX2 = 1 2s  MPI@LHC 2008 Fabrizio Ferro – INFN Genova

Soft diffraction with high b* optics = 90 m: 65 % = 1540 m: 95 % of all diffractive protons are detected, independently on their  Reconstruction of x via protons or rapidity gap (Dh= –ln x): = 90 m: sp(x) = 6 x 10-3 (without CMS vertex knowledge) = 1540 m: sp(x)  9 x 10-3 s(Dh) = 0.8 – 1  sDh(x) = (0.8 – 1) x proton 2 proton 1 Dh1 Dh2 M DPE Mass Distribution (acceptance corrected) via rapidity gap (T1, T2) s(x)/x = 100% via proton (b*=90m) via rapidity gap (CMS) via rapidity gap (T1, T2) proton resolution limited by LHC energy spread various diffractive studies (Single Diffraction and Double Pomeron Exchange) to be extended later together with CMS. MPI@LHC 2008 Fabrizio Ferro – INFN Genova

T1/T2: charged multiplicity Measurement of charged multiplicity for different processes Important also for cosmic ray physics (e.g. for MC generator validation) Identification and measurement of rapidity gaps minimum bias Acceptance: 3.1 <  < 4.7 (T1) & 5.3 <  < 6.5 (T2) () = 0.04  0.2, no mom. & limited  info dNch/dh [1/unit] Charged multiplicity single diffractive MPI@LHC 2008 Fabrizio Ferro – INFN Genova

Fabrizio Ferro – INFN Genova Multiplicity in single diffraction T1/T2 coverage Multiplicity for different x ranges: high cross sections, but partial rapidity coverage MPI@LHC 2008 Fabrizio Ferro – INFN Genova

Fabrizio Ferro – INFN Genova Conclusions Setup and optics TOTEM has partially installed its detectors and will finish the installation in the first months of 2009 ready for the new LHC start-up TOTEM measurements strongly depend on beam optics. Requested short runs at b* = 90m optics to maximize physics sensitivity. Early measurements With 90m optics: 5% measurement of stot inclusive studies of the main diffractive processes study of the elastic scattering already in a wide range of t measurement of forward charged multiplicity With low b* optics: study of SD and DPE at high masses elastic scattering at high t (t > 2 GeV2) Later A more precise measurement (1-2%) of stot will need the b*=1540m optics already foreseen for dedicated short TOTEM runs An extensive program of physics together with CMS is foreseen MPI@LHC 2008 Fabrizio Ferro – INFN Genova

Fabrizio Ferro – INFN Genova Back up MPI@LHC 2008 Fabrizio Ferro – INFN Genova

Fabrizio Ferro – INFN Genova The b* = 90 m optics Concept: Optics optimised for both elastic and diffractive scattering. Proton coordinates w.r.t. beam in the RP at 220 m: (x*, y*): vertex position (x*, y*): emission angle x = Dp/p Ly = 265m (large) vy = 0 Lx = 0 vx = – 2 D = 23mm vertical parallel-to-point focussing  optimum sensitivity to y* and hence to t (azimuth. symmetry) elimination of x* dependence enhanced sensitivity to x in diffractive events, horizontal vertex measurement in elastic events. RP (220m) hit distribution (elastic) x-projection horiz. vertex distribution (shape, width)  assuming round beams: luminosity from beam parameters  directly: beam position measurement to ~ 1mm every minute t ~ 10 s MPI@LHC 2008 Fabrizio Ferro – INFN Genova