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Latest results from the

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Presentation on theme: "Latest results from the"— Presentation transcript:

1 Latest results from the
Giornata del dipartimento di Fisica M. Berretti Siena, 21 December 2012 Latest results from the TOTEM experiment The TOTEM experiment Physics results Ongoing analyses and future

2 The TOTEM Collaboration
Siena, 21 December M. Berretti

3 TOTEM Physics Program Overview
Stand-Alone: - TOT pp with a precision ~ 1-2% (L ind. meth.) simultaneously measuring : Nel down to -t ~10-3 GeV2 and Ninel with losses < 3% - Elastic pp scattering in the range 10-3 < |t| ~ (p)2 < 10 GeV2 - Soft diffraction (SD and DPE) - Particle flow in the forward region (cosmic ray MC validation/tuning) pp elastic, inelastic and total cross section Diffractive processes Forward multiplicities Large rapidity (-ln tan q/2) gap (SD) Siena, 21 December M. Berretti

4 TOTEM CMS ALICE LHCb ATLAS LHCf The TOTEM experiment at the LHC IP5
TOTal cross section, Elastic scattering and diffraction dissociation Measurement IP5 CMS The Compact Muon Solenoid ALICE A Large Ion Collider Experiment LHCb The Large Hadron Collider beauty experiment ATLAS A Toroidal LHC ApparatuS LHCf LHC forward experiment Siena, 21 December M. Berretti

5 ALICE LHCb ATLAS LHCf The TOTEM experiment at the LHC
TOTEM is composed by 3 different detectors: T1: CSC chambers, charged particle tracking 18<q<90 mrad T2: GEM chambers, charged particle tracking 3<q<10 mrad RP: movable silicon detector: elastic and diffractive proton measurement (optics-dependent acceptance) About 99.5% of all non diffractive minimum bias events and ~85% of all diffractive events have charged particles within the acceptance of the TOTEM detectors (T1 and T2). ALICE A Large Ion Collider Experiment LHCb The Large Hadron Collider beauty experiment ATLAS A Toroidal LHC ApparatuS LHCf LHC forward experiment Siena, 21 December M. Berretti

6 Sensitivity up to 50 mm thanks to the Current Terminating Structure
The RP detector Sensitivity up to 50 mm thanks to the Current Terminating Structure One Roman Pot Beam Physical Edge 10% Efficiency 90% Efficiency A RP station: Composed by 2 units Each one with 2 Vertical and one Horizontal Pots Each Pot is equipped with 10 “edgless” silicon planes Siena, 21 December M. Berretti E.Oliveri

7 The T1 detector Installation in the CMS endcaps region
3.1 < |η| < 4.7 (h=-ln tan q/2) Cathode Strip Chambers No loss of performance after a total charge integrated on the anode wires of C/cm (5 years at a luminosity of 1030 cm−2s−1) Hit sX,Y= 1mm T1 individual arm inelastic event reconstruction efficiency : ∼98 % (at least one charged particle in T1 with pT >100 MeV/c) Siena, 21 December M. Berretti

8 IP5 The T2 detector 40 Triple Gas Electron Multiplier chambers
System set-up, commissioning and software mainly developed from the Siena group The T2 detector 40 Triple Gas Electron Multiplier chambers rmax≈14.45cm 20 Triple GEM (Minus End) IP5 rmin≈4.25cm 20 Triple GEM (Plus End) Δϕ=360o ≈13.8m ≈13.8m qmin≈3mrad ≈0.2o ≈40cm qmax≈10mrad ≈0.6o Hit sR,f= 0.1mm, 1o T2 inelastic event reconstruction efficiency : ∼99.5 % (at least one charged particle in T2 with pT >40 MeV/c) 5.3≤|h| ≤ 6.5 Siena, 21 December M. Berretti

9 The T2 detector 40 Triple Gas Electron Multiplier chambers Drift
Transit Induction GEM foil Readout Plane Installation of 2 T2 quarters Sensitive Area Δϕ=192o Advantage of a GEM plane : High tolerance to radiation (> 50 Mrad) High rate capability (> 10 MHz/cm2) Low material budget (10 planes: 0.07 X0) The large occupancy and the impossibility to resolve the pile-up vertices make T2 usable only for low luminosity runs Siena, 21 December M. Berretti

10 TOTEM Physics and results
1. Measurement of the elastic scattering on a wide range of four-momentum transfer. ~ 0.7 GeV2 ~ 1.7 GeV2 ~ |t|-7.8 ~1.5 GeV2 ISR 7 TeV Large-t region: Important for model discrimination Minimum moves to lower |t| with increasing CM energy Exponential slope grows with the CM energy Siena, 21 December M. Berretti

11 Total cross section measurement @ 7 TeV in 3 ways
stot = (98.0 ± 2.5) mb (ρ=0.14 [COMPETE]) June 2011 (EPL96): stot = (98.3 ±2.8) mb Oct (PH pre.): stot = (98.6 ±2.2) mb different bunch intensities and elastic acceptance ! stot = (99.1 ± 4.3) mb Excellent agreement between cross-section measurements at 7 TeV using - runs with different bunch intensities and RP acceptances. - different methods. Siena, 21 December M. Berretti

12 Total cross section measurement @ 7 TeV in 3 ways
Luminosity calibration: Estimated by CMS Estimated by TOTEM 1) L= 82/mb ± 4% L= 83.7/mb ± 3.8% 2) L= 1.65/mb ± 4% L= 1.65/mb ± 4.5 % Siena, 21 December M. Berretti

13 TOTEM Physics and results
1. Measurement of the pp total cross section with 1-2% systematic error by using the luminosity independent method Needs the total elastic and inelastic rate The visible elastic rate is 90%. The rest is extrapolated with the exponential fit The inelastic rate is measured triggering with T2. sinel : 72.9 ± 1.5 mb Low mass diffraction ~ 3.7% Trigger efficiency ~2.3 % T1 only events ~2% Pile-up (m~0.03) ~ 1.5 % Track reconstruction efficiency ~1% Beam-gas background ~ 0.57% Rapidity Gap in T % Central diffraction % sel =25.1±1.1 mb EPL 96 (2011) 21002 To be published dσEL/dt [mb/GeV2] -t [GeV2] Needs the extrapolation of the elastic rate to t=0 Obtained in a low luminosity run at b*=90m optics where RP edge approaches at 5s to the beam center. A = 506 ±22.7syst±1.0stat mb/GeV2 B = 19.9±0.26syst±0.04stat GeV-2 Needs the value of r (From the COMPETE collaboration fit, r= 0.14, later with a direct measurement at b*=1Km ) Siena, 21 December M. Berretti

14 σ>6.5inel= 3.7% σ<6.5inel
NB: Low mass diffraction cross-section can be constrained Estimation of σinel= σtot – σel = 73.2± 1.3mb can be done with RP-only measurement (L-dependent). However, T1+T2 visible σ<6.5inel= 70.9 ± 2.8 mb σ>6.5inel= 3.7% σ<6.5inel Needs the total elastic and inelastic rate The visible elastic rate is 90%. The rest is extrapolated with the exponential fit The inelastic rate is measured triggering with T2. sinel : 72.9 ± 1.5 mb Low mass diffraction ~ 3.7% Trigger efficiency ~2.3 % T1 only events ~2% Pile-up (m~0.03) ~ 1.5 % Track reconstruction efficiency ~1% Beam-gas background ~ 0.57% Rapidity Gap in T % Central diffraction % sEL =25.1±1.1 mb sel =25.1±1.1 mb sinel T2VIS = 95%sinel Siena, 21 December M. Berretti

15 Low mass diffraction: T1+T2 acceptance
MX > 3.4 GeV/c2 S. Ostapchenko arXiv: v2 [hep-ph] x/sSD dsSD/dx QGSJET-II-4 T1+T2 (3.1 < || < 6.5) give an unique forward charged particle LHC  lower Mdiff reachable: minimal model dependence on required corrections for low mass diffraction SIBYLL/PYTHIA8 (Mx2  s ) Several models studied: correction for low mass single diffractive cross-section based on QGSJET-II-03 (well describing low mass diffraction at lower energies), imposing observed 2hemisphere/1hemisphere event ratio and the effect of “secondaries” sMx < 3.4 GeV = 3.1 ± 1.5 mb Siena, 21 December M. Berretti

16 Cross section measurements @ 8 TeV
July 2012: runs at b* = 90 m  tot =  2.9 mb  inel = 74.7  1.7 mb Same analysis strategy as for the 7 TeV with the luminosity independent method: - Nel / Ninel =  0.011 Siena, 21 December M. Berretti

17 Forward Physics: importance of the dN/dh measurement
The CR connection: tuning of the MC generator used in the Extensive Air Showers simulations A good description of the forward particle multiplicity and density produced in p-Air collision is important for the analysis of the Extensive Air Shower produced when a High Energy CR interacts in the athmosphere. The energy and mass of the primary CR can be understood from measurement on Earth thanks to MCs which simulate the air shower. 7 TeV pp collisions at LHC correspond to pCR-pAIR collisions with pCR of ~25 PeV. Siena, 21 December M. Berretti

18 Forward Physics: importance of the dN/dh measurement
Observation of the extended longitudinal scaling: For very high energy collisions in the reference system with the target at rest, particles produced in the fragmentation region approach to a limiting distribution which doesn’t depend anymore on the collision center of mass energy. p-Gold collisions 130 GeV 19.6 GeV 200 GeV (TOTEM) Fragmentation region An universally accepted theoretical description is still missing! The theory of the Color Glass Condensate is a promising approach Siena, 21 December M. Berretti

19 Measurement of the dNCH /dh in T2
TOTEM measurements compared to MC predictions TOTEM measurements “combined” with the other LHC experiments None theoretical model fully describes the data. Cosmic Ray (CR) MCs show a better agreement for the slope: - SYBILL (CR): 4–16% lower - QGSJET-II (CR): 18-30% higher High “visible” fraction of inelastic cross section: sinel 95% sinel - Diffractive events with MDiff > 3.4 GeV - ND events > 99% Published: EPL 98 (2012) 31002 Siena, 21 December M. Berretti

20 Joint data taking with CMS
2011 Ion run: proof of principle 2012: 1st realization of common running CMS & TOTEM trigger exchange Offline data “synchronization” (orbit and bunch #) + “merging” (n-tuple level) May 2012: low pileup run: b* = 0.6 m, s1/2 = 8 TeV, T1 & T2 & CMS read out Date Trigger Inelastic events May 1 T2 || BX ~5 M no RP dN/dh, correlations, underlying event July 2012: b* = 90 m, s1/2 = 8 TeV, RP & T1 & T2 & CMS read out Date, Set Trigger Inelastic events RP position July 7, DS 2 T2 || RP2arms || BX ~2 M 6 s July 12-13, DS 3a ~10 M 9.5 s V, 11s H July 12-13, DS 3b T2 || RP2arms || CMS (CMS = 2 pT > 20GeV, m, 2 central e/g ) ~3.5 M stot, sinel with CMS, soft & semi-hard diffraction, correlations Siena, 21 December M. Berretti

21 TOTEM analyses in progress
Multiplicities Inelastic dNCH 8 TeV CMS + T2 (0 < |h| < 6.5) Inelastic dNCH /dh T1 7 TeV (3.1 < |h| < 4.7) Inelastic dNCH 8 TeV with the displaced vertex (11m) Main final state topology for inelastic events Diffractive studies Differential cross section measurement for single diffraction dsSD/dt and double diffraction dsDD/dhmin Single Diffraction Double Pomeron exchange cross section (soft and hard), exclusive jet production in CMS in double pomeron exchange Double Diffraction Double Pomeron Exchange Siena, 21 December M. Berretti

22 TOTEM analyses in progress
Elastic scattering at low-t: studied of the coulomb-nuclear interference, measurement of r a = fine structure constant = relative Coulomb-nuclear phase G(t) = nucleon el.-mag. form factor = (1 + |t| / 0.71)-2 Coulomb scattering dominant Total (Coulomb & nuclear) Coulomb-Nuclear interference Nuclear scattering dominant First (preliminary) measurement in the interference region!! Siena, 21 December M. Berretti

23 Near future (during LS1):
Extend the multiplicity analyses for each event class (ND,SD, events with Jets in CMS) . Charged particle correlations. Data taking p-Pb runs in Jan-Feb 2013 with CMS (s1/2NN=5 TeV). Multiplicity(T1+T2) and Energy flow (CASTOR & HF) in pp and pPb After LS1(2014/2015) : Repeat the stand-alone TOTEM program at the higher LHC energy Installation/Development of RP-like timing detectors (< 10 ps resolution, Cherenkow light from Quartz + SiPm) + tracking detector (pixels) : this will allow the study of the hard diffraction with CMS (combining the RP protons to the reconstructed CMS vertices) Siena, 21 December M. Berretti

24 Conclusions The TOTEM experiment at LHC is fully operative.
7 analysis-papers have been published/submitted (on the elastic, inelastic, total pp cross and 8 TeV and on the T2 dN/dh 7 TeV) Fundamental contribution of the Siena University to this success (installation and commissioning of T2, TOTEM-trigger, T2 offline and online software...). Sevaral analyses are ongoing: Large amount of work done (to do) on analysis of the multiplicties, correlations, diffractive cross sections both in pp and pA runs. Common runs already collecte with a common CMS/TOTEM trigger. Possibility to repeat the multiplicty and diffractive cross section measurements when central jets are produced. Siena, 21 December M. Berretti


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