TOTEM Results and Perspectives
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TOTEM Results and Perspectives. The TOTEM Collaboration INFN Sezione di Bari and Politecnico di Bari, Bari, Italy MTA KFKI RMKI, Budapest, Hungary Case Western Reserve University, Cleveland, Ohio,USA CERN, Geneva, Switzerland Estonian Academy of Sciences, Tallinn, Estonia

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2012 LHC Days in Split, Croatia

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2012 lhc days in split croatia

TOTEM Results and Perspectives

The TOTEM Collaboration

INFN Sezione di Bari and Politecnico di Bari, Bari, Italy

MTA KFKI RMKI, Budapest, Hungary

Case Western Reserve University, Cleveland, Ohio,USA

CERN, Geneva, Switzerland

Estonian Academy of Sciences, Tallinn, Estonia

Università di Genova and Sezione INFN, Genova, Italy

Università di Siena and Sezione INFN-Pisa, Italy

University of Helsinki and HIP, Helsinki, Finland

Academy of Sciences, Praha, Czech Republic

Elastic scattering

Total Cross-section

Inelastic cross-section

Particle Production

Diffraction

Runs with CMS

Future runs

Perspectives after the shut-down

Karsten Eggert (CWRU)

on behalf of the TOTEM collaboration

2012 LHC Days in Split, Croatia

Karsten Eggert–


2012 lhc days in split croatia

Total cross-section

Elastic Scattering

b

Cosmic Ray Physics

Diffraction: soft and hard

jet

jet

TOTEM Physics Overview

Karsten Eggert–


2012 lhc days in split croatia

Inelastic telescopes T1 and T2:

T1: 3.1 <  < 4.7

T2: 5.3 <  < 6.5

HF (CMS)

IP5

10 m

T1

CASTOR (CMS)

14 m

T2

TOTEM Detectors (T1, T2 and RP) on both sides of IP5

CMS

24 Roman Potsin the LHC tunnel on both sides of IP5

measure elastic &diffractive protons close to outgoing beam

IP5

RP147

RP220

Karsten Eggert–


Detectors

Detectors

RP 147

Package of 10 “edgeless” Si-detectors

Vertical Pot

Vertical Pot

Horizontal Pots

Vertical Pot

Vertical Pot

T2

(GEMs)

T1

(CSCs)

Karsten Eggert–


The roman pot system at 220 m

The Roman Pot System at 220 m

beam-optical elements (magnets)

ydet

scattered proton

y*

y*

beam axis

IP5

RP220

220m

Design considerations:

Two independent detection systems with 5 m lever armredundant trigger scenarios

10 Silicon detectors / RP ~ 10 mm precision

Reliable track reconstruction in both projections5 planes / projection

Determine the proton angle in both projections ~ 2 mrad precision

Approach the beam as close as possible to~ 5 – 10 s beam width

Space for adding detectors for future upgrades !!!

(x*, y*): vertex position

(x*, y*): emission angle: t  -p2 (qx* 2 + qy* 2)

x = p/p: momentum loss (diffraction)

Optimized optics

Karsten Eggert–


Proton reconstruction

Proton Reconstruction

Proton position at a given RP(x, y) is a function of position (x*, y*) and angle (Qx*, Qy*)at IP5:

measured

in Roman

Pots

Proton transport matrix

reconstructed

The effective length and magnification expressed with the phase advance:

RP

IP5

Elastic proton kinematics reconstruction (simplified):

Scattering angle reconstructed in both projections

Excellent optics understanding required

Karsten Eggert–


Beam based roman pot alignment scraping

Beam-Based Roman Pot Alignment (Scraping)

A primary collimator cuts a sharp

edge into the beam, symmetrical to

the centre

The top RP approaches

the beam until it

touches the edge

The last 10 mm step produces a spike in a Beam Loss Monitor downstream of the RP

  • When both top and bottom pots are touching the beam edge:

  • they are at the same number of sigmas from the beam centre as the collimator

  • the beam centre is exactly in the middle between top and bottom pot

     Alignment of the RPs relative to the beam

alignment is very critical and fundamental for any physics reconstruction

alignment between pots with overlapping tracks (~ few μm)

fine alignment wrt beam using elastic events

The RP – beam contacts are also registered as spikes in the trigger rate

Karsten Eggert–


2012 lhc days in split croatia

b*=3.5m (7s) b*=90m (10s) b*=90m (5s)

Sector 56

Sector 56

Aperture limitation, tmax

Beam

halo

Sector 45

t = -p2

p/p

Elastic pp scattering : proton reconstruction

Elastic ppscattering: topology (hit map in RP detectors)

y[mm]

y[mm]

Sector 45Sector56

x[mm]

x[mm]

Two diagonals analysed

independently

Karsten Eggert–

  • Both angle projections can be reconstructed:

    • Qx = L'xQ*x y = LyQ*y

    • precise values of L'x=dLx/ds and Ly @ RP locations needed

  • Need excellent optics understanding

b*=3.5m Lx~0 ; Ly~20m @220m (L=√bb*sin Dm)


Elastic scattering collinearity

Elastic Scattering: Collinearity

Collinearity in qy*

Collinearity in qx*

Scattering angle on one side versus the opposite side

Low x, i.e. |x| < 0.4 mm and 2s cut in Dqy*

|ty| (diagonal 1)

Beam divergence

|ty| (diagonal 2)

Missing acceptance inθy*

Width in agreement with beam divergence of 17 mrad

Qx is measured with 5m lever arm spectrometer

Karsten Eggert–


2012 lhc days in split croatia

Elastic pp scattering : analysis

Collinearity cut (left-right)

q*x,45↔q*x,56

q*y,45↔q*y,56

Background subtraction

Acceptance

correction

Karsten Eggert–


First measurement of the elastic pp differential cross section

2011 with b* = 3.5 m

First measurement of the elastic pp differential cross-section

First published data in 2011

EPL 95 (2011) 41001

EPL 96 (2011) 21002

Karsten Eggert–


Comparison to some models

Comparison to some models

None of the models really fit

Better statistics at large t needed (in progress)

Karsten Eggert–


Elastic pp scattering at 7 tev differential cross section t range 7 10 3 gev 2 t 3 5 gev 2

Elastic pp Scattering at 7 TeV: Differential Cross-Sectiont range : 710-3 GeV2<|t|< 3.5 GeV2

A = 506  22.7syst 1.0stat mb/GeV2

A = 503  26.7syst 1.5stat mb/GeV2

B = 19.9  0.26syst 0.04stat GeV-2

|t|dip= 0.53 GeV2

~ |t|-7.8

Integrated elastic cross-section:

Additional data set under analysis:

2 GeV2 < |t| < 3.5 GeV2

25.4 ± 1.0lumi ± 0.3syst ± 0.03stat mb (90% measured)

24.8 ± 1.0lumi ± 0.2syst ± 0.2stat mb (50% measured)

Karsten Eggert–


Low t distribution

Low t - distribution

Constant slope for

0.007 < t < 0.2 GeV2

Individual errors

Karsten Eggert–


2012 lhc days in split croatia

Slope parameter B and elastic cross-section

B constant in the range 0.007 < t < 0.2 GeV2

B increases with energy

sel / stot increases with energy

Karsten Eggert–


Elastic scattering from isr to tevatron

Elastic scattering – from ISR to Tevatron

ISR

7 TeV

~1.4 GeV2

Diffractive minimum: analogous to Fraunhofer diffraction: |t|~ p2q2

  • exponential slope B at low |t| increases

  • minimum moves to lower |t| with increasing s

  •  interaction region grows (as also seen from stot)

  • depth of minimum changes  shape of proton profile changes

  • depth of minimum differs between pp, pˉp  different mix of processes

Karsten Eggert–


Elastic scattering and total cross section at 8 tev

Elastic Scattering and Total Cross-Section at 8 TeV

July 2012: runs at b* = 90 m

only RP alignment, RPs moving

collinearity,

low x,

common vertex

Karsten Eggert–


Elastic scattering and total cross section at 8 tev1

Elastic Scattering and Total Cross-Section at 8 TeV

July 2012: runs at b* = 90 m

only RP alignment, RPs moving

Preliminary t-distributions (unnormalised)

TOTEM

preliminary

TOTEM

preliminary

  • larger |t|:

  • possible at b*=0.6m

  • difficult due to 2xSDand other background

down to |t| ~ 6 x 10-4:

foreseen at b* = 1km

Karsten Eggert–


Total inelastic cross section measurement at s 7 tev

based only on elastic scattering via optical theorem

based on the measurement of the inelastic cross-section using charged particle detectors

Inelastic cross-section is measured with two different detectors and triggers

via elastic scattering with RP detectors

via inelastic detectors

All TOTEM detectors are used

Total Inelastic Cross Section Measurement at √s = 7 TeV

Karsten Eggert–


2012 lhc days in split croatia

Direct measurement of the Inelastic Cross-Section at √s=7 TeV

T1: 3.1 <  < 4.7

T2: 5.3 <  < 6.5

Karsten Eggert–


2012 lhc days in split croatia

Inelastic Cross-Section visible in T2

Inelastic events in T2: classification

tracks in both hemispheres

non-diffractive minimum bias

double diffraction

tracks

T2

T2

tracks in a single hemisphere

mainly single diffraction

MX > 3.4 GeV/c2

η

Corrections to the T2 visible events

η

  • Trigger Efficiency: 2.3 %

  • (measured from zero bias data with respect to track multiplicity)

  • Track reconstruction efficiency: 1%

  • (based on MC tuned with data)

    • Beam-gas background: 0.54%

  • (measured with non colliding bunch data)

    • Pile-up (μ=0.03): 1.5 %

  • (contribution measured from zero bias data)

  • η

    σinelastic, T2 visible = 69.7 ± 0.1 (stat) ± 0.7 (syst) ± 2.8 (lumi) mb

    Karsten Eggert–


    2012 lhc days in split croatia

    Inelastic Cross-Section

    σinelastic, T2 visible

    σinelastic

    Missing inelastic cross-section

    • Events visible in T1 but not in T2: 2.0 %

    • (estimated from zero bias data)

    • Rapidity gap in T2 : 0.57 %

  • (estimated from T1 gap probability transferred to T2)

    • Central Diffraction: T1 & T2 empty : 0.54%

  • (based on MC, correction max 0.25σCD , quoted in systematic error)

    • Low Mass Diffraction :3.7% ± 2% (syst)

  • (Several models studied, correction based on QGSJET-II-4,

  • imposing observed 2hemisphere/1hemisphere event ratio and the effect of ‘secondaries’)

  • Possibility of measuring low mass diffraction with a single proton trigger

  • needs clean beam conditions to avoid beam halo background

  • σinelastic = 73.7 ±0.1(stat)±1.7(syst)±2.9(lumi) mb

    Karsten Eggert–

    Corrections for non visible events: tracks in T1 (& T2 empty)

    Estimated from BX data ~ 2%

    Rapidity gap in T2: estimated from T1 gap probability

    transferred to T2 h-region

    (scaled by fraction of T2 1hemi only events (no tracks in T1) taking MC

    estimated experimental rap gap survival in T2 region in account:)~ 0.5 %

    Central Diffraction: T1 & T2 empty (based on MC)

    Correction max ~ 0.25 x sCD: as cross section is unknown, quoted in syst error

    Corrections for non visible events: tracks in T1 (& T2 empty)

    Estimated from BX data ~ 2%

    Rapidity gap in T2: estimated from T1 gap probability

    transferred to T2 h-region

    (scaled by fraction of T2 1hemi only events (no tracks in T1) taking MC

    estimated experimental rap gap survival in T2 region in account:)~ 0.5 %

    Central Diffraction: T1 & T2 empty (based on MC)

    Correction max ~ 0.25 x sCD: as cross section is unknown, quoted in syst error


    2012 lhc days in split croatia

    MX>3.4 GeV/c2 (T2 acceptance)

    S. Ostapchenko

    arXiv:1103.5684v2 [hep-ph]

    x/sSDdsSD/dx

    QGSJET-II-4

    SIBYLL/PYTHIA8

    low mass contribution

    Inelastic Cross Section : low mass diffraction

    Correction based on QGSJET-II-4

    sMx < 3.4 GeV = 2.7 ± 1.5 mb

    • By comparison with the measured inelastic cross-section (using the total cross-section)

    • the low mass single diffraction can be determined:

    • stot – sel = 73.2 ± 1.3 mb

    • Mx < 3.4 GeV = 2.2 ± xx mb (preliminary)

    • Possibility of measuring low mass diffraction with a single proton trigger

    • needs clean beam conditions to avoid beam halo background

    Karsten Eggert–


    3 ways to the total cross section

    3 Ways to the Total Cross-Section

    stot= (98.0 ± 2.5) mb

    (ρ=0.14[COMPETE])

    June 2011 (EPL96): stot = (98.3 ±2.8) mb

    Oct. 2011 (PH pre.): stot = (98.6 ±2.2) mb

    different bunch intensities !

    stot= (99.1 ± 4.3) mb

    Excellent agreement between cross-section measurements at 7 TeV using

    - runs with different bunch intensities,

    - different methods.

    Karsten Eggert–


    2012 lhc days in split croatia

    Cross-sections with different methods

    COMPETE extrapolation: r = 0.141  0.007

    done before TOTEM measurement

    Karsten Eggert–


    2012 lhc days in split croatia

    Luminosity determination and ratios

    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 %

    Luminosity and ρ independent ratios:

    σel/ σtot = 0.257 ± 2% σel/ σinel=0.354 ± 2.6%

    Summary:

    The cross-section measurements are in excellent agreement using:

    runs with different bunch luminosities

    different methods

    Karsten Eggert–


    A first very crude r estimate at 7 tev

    A First, Very Crude r Estimate at 7 TeV

    From optical theorem:

    r < 0.32 (95% CL),

    or, using Bayes’ approach (with uniform prior |r| distribution):

    |r| = 0.145  0.091[COMPETE extrapolation: r = 0.141  0.007]

    E710/E811: r = 0.135 ± 0.044

    TOTEM, 7 TeV

    Not so exciting, but …

    Karsten Eggert–


    R measurement elastic scattering at low t

    r Measurement: Elastic Scattering at Low |t|

    Optical Theorem:

    Total (Coulomb & nuclear)

    Coulomb scattering dominant

    Coulomb-Nuclear interference

    Nuclear scattering

    • a= fine structure constant

    • = relative Coulomb-nuclear phase

      G(t) = nucleon el.-mag. form factor = (1 + |t| / 0.71)-2

      r=  /  [Telastic,nuclear(t = 0)]

    Measurement of r by studying the Coulomb – Nuclear interference region down to

    |t| ~ 6 x 10-4 GeV2

    Reachable with b* ~ 1000 m still in 2012 if RPs can approach beam centre to ~ 4s

    Karsten Eggert–


    How to reach the coulomb nuclear interference region

    How to reach the Coulomb-Nuclear Interference Region ?

    RP window position

    (real s for en=2mm rad)

    √s = 8 TeV

    √s = 13 TeV

    push b* to > 2000 m

    good t-resolution needs parallel-to-point focussing

    in both x and y (phase advance p/2)

    RP approach the beam to ~ 4 s

    Beam emittance en < 2 mm rad

     Challenging but possible

    Additional magnet cables needed. To be installed during LS1

    Karsten Eggert–


    The b 1000 m optics

    The b* = 1000 m Optics

    MD in June: first unsqueeze to 1km achieved

    14 September:

    • special beam optics with b* = 1000 m fully commissioned

    • collisions in IP1 and IP5 found

    • vertical emittances en ~ 2 mm rad

    • 4 vertical TOTEM RPs (out of 8) aligned at ~4 s

    • time slot ended  no physics data taken yet, diagnostic data on halo background being analysed

    • Physics run scheduled for October 2012

    Karsten Eggert–


    2012 lhc days in split croatia

    Perspectives on Diffractive Physics, e.g. Double Pomeron Exchange

    MPP2 = 12s

    Rapidity Gap

    Dh =-ln1

    -ln2

    CMS

    h

    TOTEM

    Scattered proton

    Scattered proton

    • β* = 90m optics runs:

    • DPE protons of -t > 0.02GeV2 detected by RP

    • nearly complete ξ-acceptance

    • σDPE measurement method:

    Karsten Eggert–


    2012 lhc days in split croatia

    Correlation between the forward proton(s) and particles in T2

    DP

    SD

    (low x)

    Karsten Eggert–


    Single diffraction large x

    Single diffraction large x

    Single diffraction large x

    Rapidity Gap

    Dh = -ln

    MX2 =  s

    h

    Karsten Eggert–


    Diffractive analyses ongoing

    Diffractive Analyses Ongoing

    T2

    T1

    T1

    T2

    Based on b* = 90 m (7 TeV) run in Oct. 2011 (RP @ 4.8s – 6.5s):

    • Central Diffraction(d2sDPE / dt1 dt2, sDPE )

    • Single Diffraction(dsSD/dt , dsSD/dx , sSD )

    • Double DiffractionSelect diff. masses 3.4 GeV < M < 10 GeV requiring tracks in both T2s, veto on T1s

     Extend studies over full h range with CMS (2012 data)

    Karsten Eggert–


    Charged particle pseudorapidity density dn d h

    Charged Particle Pseudorapidity Density dN / dh

    T2

    [T1]

    EPL 98 (2012) 31002

    • Analyses in progress:

    • T1 measurement at 7 TeV (3.1 < |h| < 4.7)

    • NEW: combined analysis CMS + TOTEM (0 < |h| < 6.5) on low-pileup run of 1st May 2012 (8 TeV): common trigger (T2, bunch crossings), both experiments read out

    • NEW: parasitical collision at b* = 90 m (7 July 2012)

    •  vertex at ~11m  shifted h acceptance:

    Karsten Eggert–


    Joint data taking with cms

    Joint Data Taking with CMS

    • Realisation of common running much earlier than ever anticipated

    • Hardware: electrical from RP220 to CMS  trigger within CMS latency

    • Trigger: bi-directional level-1 exchange  same events taken

    • Synchronisation: orbit number and bunch number in data streams

    • Offline:- common repository for independently reconstructed data- merging procedure  common n-tuples

    Karsten Eggert–


    Joint data taking with cms1

    Joint Data Taking with CMS

    May 2012: low pileup run: b* = 0.6 m, s = 8 TeV, T1 & T2 & CMS read out

    dN/dh,

    correlations,

    underlying event

    July 2012: b* = 90 m, s = 8 TeV, RP & T1 & T2 & CMS read out

    stot, sinel with CMS,

    soft & semi-hard diffraction,

    correlations

    • Abundant material for analysis activities throughout LS1

    • Analyses starting:

    • hard diffraction: p + dijets (90m runs)

    • combined dNch / dh and multiplicity correlations

    Karsten Eggert–


    Runs planned for 2012 2013

    Runs Planned for 2012 / 2013

    • b* = 1000 m: scheduled for 24 October study interference region, measure r

    • RP insertions in normal physics runs (b* = 0.6 m) - hard diffraction together with CMS (high diffractive masses reachable) - study of closest possible approach of the horizontal RPs (i.e. acceptable beam losses) essential for all near-beam detector programmes at high luminosity after LS1

      • Collimators needed behind the RP to protect quadrupoles

    • request a low-pileup run (m ~ 5 %) with RPs at b* = 0.6 m (in May RPs were not aligned) study soft central diffraction final states with 2 leading protons defining Pomeron-Pomeron mass M2 = x1 x2 sgood x resolution at b* = 0.6 m s(M) ~ 5 GeV

    • participation in the p-Pb runs with insertions of the RPs on the proton side  study diffractive/electromagnetic and quasi-elastic p-Pb scatteringp-Pb test run in September with CMS was successful(T2 trigger given to CMS)

    Karsten Eggert–


    2012 lhc days in split croatia

    To be done this year

    Together with CMS studies on:

    Rapidity distribution over the full acceptance range

    Diffractive di-jets

    Double Pomeron Exchange

    Single Diffraction

    Double Diffraction

    Elastic scattering and cross-sections at √s = 8 TeV

    Measurement of r with b*=1000 m

    Preparation for Diffractive Di-jet production at highest luminosities in view of the new forward set-up after LS1

    p-A data taking in 2013

    Finalize the three papers in the pipe-line

    Karsten Eggert–


    The end

    The End

    Karsten Eggert–


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