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

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$Diffraction Dissociation at the LHC Marco$ Bozzo INFN Genova and University of Genova

1 Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC Marco Bozzo INFN Genova and University of Genova (Italy) on behalf of the TOTEM Collaboration

2 Overview: The experiment and the detectors First observations with the inelastic telescopes Measurement of large-t pp elastic scattering ( GeV 2 ) A look at diffractive and DPE events with TOTEM p. 2

3 TOTEM Physics Overview Total cross-section Elastic Scattering b Forward physics L L tot 2 tot elastic dn dt N N t 0 inelastic Optical Theorem tot ( dn N el / dt) N t 0 inel Diffraction: soft and hard b je t jet p. 3

4 The TOTEM detector set-up 3.1 h h 6.5 T1 T2 p. 4

5 T1 and T2 in the forward region of CMS T1 telescope 5 planes of CSC chambers Wires and cathode strips T2 telescope 10 planes of GEM chambers Strips and pads p. 5

6 Preliminary dn/dh results (T2) Low luminosity runs 2010 T2 plus and minus sides superimposed Raw data s 7 TeV Unfolded data Data taken during scraping exercise And with low intensity bunches of p (low pile-up) Green band = data after vertex cuts p. 6

7 First data (T1) Telescope installed in shutdown So far short periods of data taking with low luminosity (L = cm 2 s 1 ) [March (2.76 TeV), May (7 TeV) ] Detector working Data analysis in progress Vertex reconstruction h Distributions (uncorrected) 7 TeV Vertex reconstruction is affected by the CMS magnetic field. p. 7

8 PP ELASTIC SCATTERING t-range: GeV 2 p. 8

9 The Roman Pot Unit BPM Vertical Pots Horizontal Pot p. 9

10 2010 Runs Topology near and far units diagonals Low selection (3σ) x RP,45 <3σ L x,45 =0 x RP,56 <3σ L x,56 =0 corr. y RP216,45 y RP220,45 corr. y RP216,56 y RP220,56 Elastic colinearity (3σ) θ x,45 * θ x,56 * θ y,45 * θ y,56 * Only 220 moved close to the beams - vertical 7σ ~ 3 mm from circulating beams - low pile-up Integrated luminosity : 6.2 nbarn -1 Total triggers 5.28M Reconstructed tracks & elastic topology 293k Low selection 70.2k Collinearity cuts 66.0k Diagonals analysed independently p. 10

Proton reconstruction Both angle projections reconstructed: Θ x * and Θ y * Θ x * from Θ x @ RP220 (through dl x /ds) Θ x = dl x /ds Θ x * Θ y * from y @ RP220 (through L y ) y = L y Θ y * Excellent

11 Proton reconstruction Both angle projections reconstructed: Θ x * and Θ y * Θ x * from Θ RP220 (through dl x /ds) Θ x = dl x /ds Θ x * Θ y * from RP220 (through L y ) y = L y Θ y * Excellent beam optics understanding Magnet currents measured Measurements of actual beam optics parameters with elastic scattering Θ left * = Θ right * (proton pair colinearity) Proton position angle correlations L x =0 determination, coupling corrections Fine geometric alignment Alignment between pots with overlapping tracks ( 1μm) Alignment with respect to the beam scraping exercise ( 20μm) Mechanical constraints between top and bottom pots ( 10μm) Track based alignment p. 11

12 Proton tracks in one diagonal (left-right coincidences) Sector 56 t = -p 2 q 2 Dp/p Sector 45 y = L y Q y x = L x Q x + D L x ~ 0 p. 12

13 Low = Dp/p cuts x < 3σ L x = 0 y RP near,45 y RP far,45 (dly/ds 0) p. 13

14 Elastic colinearity cuts Data outside the 3σ cuts used for background estimation p. 14

15 t y -acceptance corrections Resolution Missing acceptance in θ y * t <0.36GeV 2 removed Resolution : compatible with beam divergence of 17 mrad p. 15

-acceptance correction Accepted (t) Diagonal 1 1 2 3 4 5 6 Θ * Total -acceptance correction No. t [GeV 2 ] Θ * [rad] Accepted (2 diag.) [ ] accept. correct. factor 1 0.33 1.65E-04 38.6 9.3 2 0.36 1.

16 -acceptance correction Accepted (t) Diagonal Θ * Total -acceptance correction No. t [GeV 2 ] Θ * [rad] Accepted (2 diag.) [ ] accept. correct. factor E E E E E E Accepted (t) Diagonal 2 t <0.36GeV 2 removed Critical at low t-acceptance limit p. 16

17 Efficiency determination Method 3 out of 4 : full elastic analysis with 3 T (track segments) instead of 4 (56 far) 3 pots out of 4 used to determine efficiency of missing pot 4 pot-diagonal efficiency computed via consequent combinations Studied Correlated pots inefficiencies for 2T/4 Determine inefficiency in detection of pp Efficiency correction t-independent = >>> breakdown of triggers : ~90% on background (showers) ; ~5% cut by RP acceptance ; ~5% pp pairs p. 17

18 Background and resolution determination signal background combined B/S = (8±1)% σ * =17.8 mrad (beam divergence) Data Combined background (t) Dθ x /sqrt(2) Signal to background normalisation σ * t-reconstruction resolution: ( t) t (also as a function of Dθ y ) * 2 p t : 0.4 GeV 1GeV 3 GeV :14% :8.8% :5.1% -t [GeV 2 ] Signal vs. background (t) t =0.4GeV 2 : B/S = (11±2)% t =0.5GeV 2 : B/S = (19±3)% t =1.5GeV 2 : B/S = (0.8±0.3)% p. 18

19 Differential pp cross-section EPL, 95 (2011) p. 19

20 Statistical and Systematic uncertainties for the t and d /dt results p. 20

$5 GeV 2 Diffractive minimum: analogous to Fraunhofer diffraction: t ~p 2 q 2 exponential slope B at low t increases minimum moves to lower t with increasing s interaction region grows (as also seen$

21 pp Elastic Scattering - ISR to Tevatron ISR ~ 1.7 GeV 2 ~ 0.7 GeV 2 ~0.5 GeV 2 Diffractive minimum: analogous to Fraunhofer diffraction: t ~p 2 q 2 exponential slope B at low t increases minimum moves to lower t with increasing s interaction region grows (as also seen from s tot ) depth of minimum changes shape of proton profile changes depth of minimum differs between pp, pˉp different mix of processes p. 21

22 Comparison with models B (t=-0.4 GeV 2 ) t DIP t -x [1.5 2 GeV 2 ] Islam Jenkovsky Petrov Bourrely Block TOTEM 23.6 ± ± ± 0.3 p. 22

23 DIFFRACTIVE EVENTS p. 23

$q/2 Single Diffraction M Double Diffraction Double Pomeron Exchange M p.$

24 Dominant Event Classes in p-p Collisions Elastic Scattering h = - ln tan q/2 Single Diffraction M Double Diffraction Double Pomeron Exchange M p. 24

25 Single diffraction low Correlation between leading proton and forward detector T2 SD Rapidity Gap Dh = -ln M X 2 = s h sector 45 IP sector 56 RP T2 T2 RP Low <0.15% p. 25

26 Single diffraction large correlation between leading proton and forward detector T2 SD Rapidity Gap Dh = -ln M X 2 = s sector 45 IP sector 56 h RP T2 T2 RP Large >6.5% p. 26

27 Double Pomeron Exchange (DPE) DPE Rapidity Gap Dh -ln 1 M PP 2 = 1 2 s -ln 2 h -ln tan q/2 USE the LHC as a Pomeron-Pomeron (Gluon - Gluon) Collider p. 27

28 Double Pomeron Exchange correlation between leading proton and forward detector T2 sector 45 IP sector 56 RP T2 T2 RP low ξ high ξ <1.5% >1.5% p. 28

29 First attempt at DPE Mass Reconstruction 1 < 1.5%; 2 > 5.0% Mass [GeV] p. 29

30 Summary The TOTEM detector is fully installed and has started to produce Physics results Measurement of elastic scattering for t between.36 and 2.5 GeV2 the dip in proton proton has been clearly observed, data have been published Measurement of total cross section T2 telescope: preliminary distribution dn/dh T1 telescope: ready to do physics The potentiality of the combined system of RP and inelastic telescopes to observe and measure Single diffractive and Double Pomeron Exchange events has been demonstrated. p. 30

31 Thank you for your attention Our data are now published in EPL, 95 (2011) p. 31

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

$Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC$ Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC Marco Bozzo INFN Genova e Universita di Genova (Italy) [for the TOTEM collaboration] Marco Bozzo 1 Outlook The TOTEM experiment