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2012 LHC Days in Split, Croatia

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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

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–

Total cross-section

Elastic Scattering

b

Cosmic Ray Physics

Diffraction: soft and hard

jet

jet

TOTEM Physics Overview

Karsten Eggert–

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–

RP 147

Package of 10 “edgeless” Si-detectors

Vertical Pot

Vertical Pot

Horizontal Pots

Vertical Pot

Vertical Pot

T2

(GEMs)

T1

(CSCs)

Karsten Eggert–

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 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–

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–

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)

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–

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–

2011 with b* = 3.5 m

First published data in 2011

EPL 95 (2011) 41001

EPL 96 (2011) 21002

Karsten Eggert–

None of the models really fit

Better statistics at large t needed (in progress)

Karsten Eggert–

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–

Constant slope for

0.007 < t < 0.2 GeV2

Individual errors

Karsten Eggert–

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–

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–

July 2012: runs at b* = 90 m

only RP alignment, RPs moving

collinearity,

low x,

common vertex

Karsten Eggert–

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–

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

Karsten Eggert–

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

T1: 3.1 < < 4.7

T2: 5.3 < < 6.5

Karsten Eggert–

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%

- Beam-gas background: 0.54%

- Pile-up (μ=0.03): 1.5 %

η

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

Karsten Eggert–

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 %

- Central Diffraction: T1 & T2 empty : 0.54%

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

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

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–

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–

Cross-sections with different methods

COMPETE extrapolation: r = 0.141 0.007

done before TOTEM measurement

Karsten Eggert–

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–

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–

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–

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–

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–

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

MPP2 = 12s

Rapidity Gap

Dh =-ln1

-ln2

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–

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

DP

SD

(low x)

Karsten Eggert–

Single diffraction large x

Rapidity Gap

Dh = -ln

MX2 = s

h

Karsten Eggert–

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–

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–

- 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–

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–

- 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–

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–

Karsten Eggert–