1. 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–

2. TOTEM Physics Overview
Total cross-section b
Elastic Scattering
Cosmic Ray Physics
jet 
Diffraction: soft and hard
Karsten Eggert–

3. TOTEM Detectors (T1, T2 and RP) on both sides of IP5
Inelastic telescopes T1 and T2:
IP5
T1: 3.1 <  < 4.7
T2: 5.3 <  < 6.5
10 m
14 m T1
CASTOR (CMS)
HF (CMS) T2
CMS
24 Roman Pots in the LHC tunnel on both sides of IP5
measure elastic & diffractive protons close to outgoing beam
IP5
RP147
RP220
Karsten Eggert– 3

4. Detectors RP 147 T2 T1 (GEMs) (CSCs)
Package of 10 “edgeless” Si-detectors
Vertical Pot
Vertical Pot
Horizontal Pots
Vertical Pot
Vertical Pot T1
(CSCs) T2
(GEMs)
Karsten Eggert–

5. The Roman Pot System at 220 m
Design considerations:
Two independent detection systems with 5 m lever arm redundant trigger scenarios
10 Silicon detectors / RP ~ 10 mm precision
Reliable track reconstruction in both projections 5 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 !!!
ydet y*
IP5
y*
RP220
220m
beam axis
scattered proton
beam-optical elements (magnets)
(x*, y*): vertex position
(x*, y*): emission angle: t  -p2 (qx* 2 + qy* 2)
x = p/p: momentum loss (diffraction)
Beam vertex
Angular beam divergence
Min. reachable |t|
Standard optics
b* ~ 1 m
sx,y* small
s(qx,y*) large
|tmin| ~ 0.3–1 GeV2
Special optics
b* = 90 m
sx,y* large
s(qx,y*) small
|tmin| < 10-2 GeV2
Optimized optics
Karsten Eggert–

6. Proton Reconstruction
Proton position at a given RP (x, y) is a function of position (x*, y*) and angle (Qx*, Qy*) at IP5: RP
IP5
measured
in Roman
Pots
reconstructed
Proton transport matrix
The effective length and magnification expressed with the phase advance:
Elastic proton kinematics reconstruction (simplified):
Scattering angle reconstructed in both projections
Excellent optics understanding required
Karsten Eggert–

7. 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–

8. Elastic pp scattering: topology (hit map in RP detectors)
Elastic pp scattering : proton reconstruction
Sector 56
Sector 45
Aperture limitation, tmax
Beam
halo
b*=3.5m (7s) b*=90m (10s) b*=90m (5s)
y[mm]
y[mm]
Sector Sector 56
x[mm]
x[mm]
t = -p2 
p/p
Two diagonals analysed
independently
Karsten Eggert–
Both angle projections can be reconstructed:
Qx = L'x Q*x y = LyQ*y
precise values of L'x=dLx/ds and RP locations needed
Need excellent optics understanding
b*=3.5m Lx~0 ; (L=√bb* sin Dm)

9. 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*
Missing acceptance in θy*
Beam divergence
|ty| (diagonal 2)
|ty| (diagonal 1)
Width in agreement with beam divergence of 17 mrad
Qx is measured with 5m lever arm spectrometer
Karsten Eggert–

10. 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–

11. First measurement of the elastic pp differential cross-section
2011 with b* = 3.5 m
First published data in 2011
EPL 95 (2011) 41001
EPL 96 (2011) 21002
Karsten Eggert–

12. Comparison to some modelsB
(t=-0.4 GeV2)
tDIP
t-n
[1.5–2.5 GeV2]
20.2
0.60
5.0
23.3
0.51
7.0
22.0
0.54
8.4
25.3
0.48
10.4
20.1
0.72
4.2
23.6 ± 0.5
0.53 ± 0.01
7.8 ± 0.3
None of the models really fit
Better statistics at large t needed (in progress)
Karsten Eggert–

13. Elastic pp Scattering at 7 TeV: Differential Cross-Section t 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–

14. Low t - distribution Constant slope for 0.007 < t < 0.2 GeV2
Individual errors
Karsten Eggert–

15. Slope parameter B and elastic cross-section
B constant in the range < t < 0.2 GeV2
B increases with energy
sel / s tot increases with energy
Karsten Eggert–

16. Elastic scattering – from ISR to Tevatron
~1.4 GeV2
Diffractive minimum: analogous to Fraunhofer diffraction: |t|~ p2 q2
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–

17. 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–

18. 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 2xSD and other background
down to |t| ~ 6 x 10-4:
foreseen at b* = 1km
Karsten Eggert–

19. 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
Karsten Eggert–

20. Direct measurement of the Inelastic Cross-Section at √s=7 TeV
Karsten Eggert–

21. Inelastic Cross-Section visible in T2
Inelastic events in T2: classification T2 η
tracks
tracks in both hemispheres
non-diffractive minimum bias
double diffraction
tracks in a single hemisphere
mainly single diffraction
MX > 3.4 GeV/c2
Corrections to the T2 visible events
Trigger Efficiency: %
(measured from zero bias data with respect to track multiplicity)
Track reconstruction efficiency: 1%
(based on MC tuned with data)
Beam-gas background: %
(measured with non colliding bunch data)
Pile-up (μ =0.03): %
(contribution measured from zero bias data)
σinelastic, T2 visible = 69.7 ± 0.1 (stat) ± 0.7 (syst) ± 2.8 (lumi) mb
Karsten Eggert–

22. Inelastic Cross-Section
σinelastic, T2 visible
σinelastic
Missing inelastic cross-section
Events visible in T1 but not in T2: %
(estimated from zero bias data)
Rapidity gap in T2 : %
(estimated from T1 gap probability transferred to T2)
Central Diffraction: T1 & T2 empty : %
(based on MC, correction max 0.25σCD , quoted in systematic error)
Low Mass Diffraction : % ± 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

23. Correction based on QGSJET-II-4
Inelastic Cross Section : low mass diffraction
MX>3.4 GeV/c2 (T2 acceptance)
x/sSD dsSD/dx
SIBYLL/PYTHIA8
QGSJET-II-4
low mass contribution
S. Ostapchenko
arXiv: v2 [hep-ph]
Correction based on QGSJET-II-4
s Mx < 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:
s tot – s el = 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–

24. 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 (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–

25. Cross-sections with different methods
COMPETE extrapolation: r =  0.007
done before TOTEM measurement
Karsten Eggert–

26. 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 = ± 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–

27. A First, Very Crude r Estimate at 7 TeV
From optical theorem:
r < (95% CL),
or, using Bayes’ approach (with uniform prior |r| distribution):
|r| =  [COMPETE extrapolation: r =  0.007]
E710/E811: r = ± 0.044
TOTEM, 7 TeV
Not so exciting, but …
Karsten Eggert–

28. 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– 28

29. How to reach the Coulomb-Nuclear Interference Region ?
√s = 8 TeV
√s = 13 TeV
RP window position
(real s for en=2mm rad)
RP approach the beam to ~ 4 s
Beam emittance en < 2 mm rad
 Challenging but possible
push b* to > 2000 m
good t-resolution needs parallel-to-point focussing
in both x and y (phase advance p/2)
Additional magnet cables needed. To be installed during LS1
Karsten Eggert–

30. 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–

31. Perspectives on Diffractive Physics, e.g. Double Pomeron Exchange
CMS
TOTEM
MPP2 = 1 2s
-ln 2
Rapidity Gap
Dh =-ln 1 h
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–

32. Correlation between the forward proton(s) and particles in T2SD
(low x)
Karsten Eggert–

33. Single diffraction large x
Rapidity Gap
Dh = -ln 
MX2 =  s h
Karsten Eggert–

34. Diffractive Analyses Ongoing
Based on b* = 90 m (7 TeV) run in Oct s – 6.5s):
• Central Diffraction (d2sDPE / dt1 dt2, sDPE )
• Single Diffraction (dsSD/dt , dsSD/dx , sSD )
• Double Diffraction Select 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) T1 T2
Karsten Eggert–

35. Charged Particle Pseudorapidity Density dN / dh
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–

36. 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–

37. Joint Data Taking with CMS
May 2012: low pileup run: b* = 0.6 m, s = 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, s = 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
Abundant material for analysis activities throughout LS1
Analyses starting:
hard diffraction: p + dijets (90m runs)
combined dNch / dh and multiplicity correlations
Karsten Eggert–

38. 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 s good 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 scattering p-Pb test run in September with CMS was successful (T2 trigger given to CMS)
Karsten Eggert–

39. To be done this year Diffractive di-jets Double Pomeron Exchange
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–

40. The End
Karsten Eggert–