1. Risultati e Prospettive dell’EsperimentoTOTEM
Giuseppe Latino
(Firenze University & INFN)
(on behalf of the TOTEM Collaboration)
SIF 2015
Roma – September 24, 2015
G. Latino – Risultati e Prospettive dell’Esperimento TOTEM
1/27

2. G. Latino – Risultati e Prospettive dell’Esperimento TOTEM
Overview
TOTEM physics programme
TOTEM LHC
LHC-Run I TOTEM physics results
TOTEM upgrade programme
Summary
2/27
SIF 2015 – 24/09/15
G. Latino – Risultati e Prospettive dell’Esperimento TOTEM

3. TOTEM @ CERN Large Hadron Collider (LHC)
- Total Cross Section - Elastic Scattering - Diffractive Dissociation
Beam 1
Proton – Proton
Collisions
Beam 2
CMS
TOTEM
IP5
LHC b
IP2
IP8
LHC f
MoEDAL
ALICE
IP1
LHC - p-p collisions at s up to 14 TeV - Linst up to ~ 1034 cm-2s-1 - started in Fall experiments
ATLAS
SIF 2015 – 24/09/15
G. Latino – Risultati e Prospettive dell’Esperimento TOTEM
3/27

4. TOTEM Physics Program Overview
Stand-Alone
- TOTpp with a precision ~ 1-2%, simultaneously measuring (L ind. meth.):
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)
CMS-TOTEM
(CMS/TOTEM Physics TDR, CERN/LHCC /G-124)
- Soft and hard diffraction in SD and DPE (production of jets, bosons, h.f.)
- Central exclusive particle production
- Low-x physics
- Particle and energy flow in the forward region
4/27
SIF 2015 – 24/09/15
G. Latino – Risultati e Prospettive dell’Esperimento TOTEM

5. LHC, inelastic collisions
CMS/TOTEM Program M
Double Pomeron Exchange
Double Diffraction
Single Diffraction
Elastic Scattering
~ 60 mb
~ 25 mb
~ 10 mb
~ 5 mb
~ 1 mb
<< 1 mb
@ 7 TeV
(MC)
Charged particles
Energy flux
TOTEM+CMS
dE/dh
dNch/dh
Roman Pots
T1,T2
LHC, inelastic collisions
CMS
CMS + TOTEM  largest acceptance detector ever built at a hadron collider:
the large  coverage and p detection on both sides allow the study of a wide
range of physics processes in diffractive
interactions
G. Latino – Risultati e Prospettive dell’Esperimento TOTEM
5/27
SIF 2015 – 24/09/15

6. Three Methods for T Measurement
Optical Theorem:
 =  (from Compete)
COMPETE Coll. [PRL 89, (2002)]
(~ ln2 s ) T
1) Elastic Scattering + Inelastic Scattering + L :
no dependence on ρ
2) Elastic Scattering + L + Optical Th.:
no dependence on Ninel
3) Elastic Scattering + Inelastic Scattering + Optical Th.:
L -independent
Proper tracking acceptance in very forward region required: elastically scattered p detection mandatory
6/27
SIF 2015 – 24/09/15
G. Latino – Risultati e Prospettive dell’Esperimento TOTEM

7. Angular divergence @ IP: Minimal reachable |t|:
Elastic Scattering Cross Section LHC
Diffractive structure
Photon - Pomeron interference  
Multigluon (“Pomeron”) exchange  e– B |t|
Wide range of predictions;
big uncertainties at large |t|.
 Importance of measuring whole |t| range with good statistics
 t  p2 2
Angular IP:
* = (/*)
Beam IP:
* = (*)
Minimal reachable |t|:
|tmin| = n2p2/*
pQCD  |t|–k
Allowed |t| range depends on beam optics
(special high *– lowL runs required for low |t|)
and on proton detector approach to the beam
SIF 2015 – 24/09/15
G. Latino – Risultati e Prospettive dell’Esperimento TOTEM
7/27

8. Inelastic Telescopes:
TOTEM Detector IP5 of LHC (Same of CMS)
T1:3.1 << 4.7
T2: 5.3 <  < 6.5
Inelastic Telescopes:
reconstruction of tracks and interaction vertex;
trigger capability with acceptance > 95 %
T1: mrad
T2: mrad
h = - log(tg(/2)) 
Detectors on both sides of IP5
CMS HF HF
~14 m
10.5 m T1 T2
RP220
(RP147)
ZDC
Elastic Detectors (Roman Pots): reconstruction of elastically scattered and diff. p
Active area up mm from beam: 5-10 rad
8/27
SIF 2015 – 24/09/15
G. Latino – Risultati e Prospettive dell’Esperimento TOTEM

9. G. Latino – Risultati e Prospettive dell’Esperimento TOTEM
TOTEM Detectors
hit  10 µm
Package of 10 “edgeless” Si-detectors
Vertical Pot
Horizontal Pots
RP 147
T2 (GEMs)
hit  100 µm
T1 (CSCs)
hit  1 mm
SIF 2015 – 24/09/15
G. Latino – Risultati e Prospettive dell’Esperimento TOTEM
9/27

10. Proton Transport from IP5 to RP Location
ydet y*
IP5
y*
RP220
220m
beam axis
scattered proton
beam-optical elements (magnets)
Optical functions:
L (effective length), v (magnification), D (machine dispersion)
- Describe the explicit path of particles
through the magnetic elements as a function
of the particle parameters at IP
- Define t and -range (acceptance)
- Depend on LHC machine optics configuration RP
IP5
Measured in RP
Reconstructed
Proton transport matrix
With:  = p/p; t = tx + ty; ti ~ -(pi*)2
(x, y): vertex position at RP location (s)
(x*, y*): vertex position at IP
(x*,y*): emission angle at IP
(x measured with  5m lever
arm spectrometer)
 Elastic proton kinematics
reconstruction (x*,y*)
(for b* = 90 RP220m:
Ly = 263 m, vy  0, Lx  0, vx = -1.9 ):
Excellent optics determination ( 0.25% using constraints from proton tracks in RPs, New J. Phys. 16 (2014) ) and detector alignment required
SIF 2015 – 24/09/15
G. Latino – Risultati e Prospettive dell’Esperimento TOTEM
10/27

11. G. Latino – Risultati e Prospettive dell’Esperimento TOTEM
Elastic Scattering Cross Section 7 TeV
Data taking in various
LHC configurations and
different RP detector
approach to the beam
allowed the measurement
in a wide range of |t|:
5· GeV2
Data Set
β*(m)
RP approach (beam )
Lint (µb-1)
|t|- range (GeV2)
Elastic events
Reference 1 90
4.8 – 6.5 83
5·10-3 – 0.4 1M
EPL 101 (2013), 21002 2 10
1.7
0.02 – 0.33
15K
EPL 96 (2011), 21002 3
3.5 7
6.1·103
0.36 – 2.5
66K
EPL 95 (2011), 41001 4 18
2.3·106
2 – 3.5
10K
Ongoing
SIF 2015 – 24/09/15
G. Latino – Risultati e Prospettive dell’Esperimento TOTEM
11/27

12. del/d|t| Measurement @ 7 TeV: Results
A = 506  23.0syst  0.9stat mb/GeV2
A = 504  26.7syst  1.5stat mb/GeV2
B = 19.9  0.27syst  0.03stat GeV-2
|t|dip= 0.53 GeV2
~ |t|-7.8
None of the theoretical models
really fit the data
EPL 95 (2011) 41001
EPL 96 (2011) 21002
EPL 101 (2013) 21002
Analysis ongoing on additional
data set (2 GeV2 < |t| < 3.5 GeV2)
Integrated elastic cross-section: El = El, Meas. + El, Extr.
(L from CMS, with 4% unc.)
el = 25.4 ± 1.0lumi ± 0.3syst ± 0.03stat mb (91% directly measured)
el = 24.8 ± 1.0lumi ± 0.7syst ± 0.2stat mb (67% directly measured)
SIF 2015 – 24/09/15
G. Latino – Risultati e Prospettive dell’Esperimento TOTEM
12/27

13. Direct inel Measurement @ 7 TeV: inel = Ninel /L
MX > 3.4 GeV/c2 (TOTEM)
x/sSD dsSD/dx
SIBYLL / PYTHIA8
QGSJET-II-4
low mass contribution
S. Ostapchenko
arXiv: v2 [hep-ph]
MX > 15.7 GeV/c2
(ALICE, ATLAS, CMS)
Impact of Low-Mass diffraction:
Extrapolation to low MX region: main
source of systematic uncertainty on inel
Minimal MX depends on maximal ||
coverage: lower MX reachable  minimal model
dependence on corrections for low mass diffraction
TOTEM (T1+T2: 3.1 < || < 6.5) gives an unique
forward charged particle LHC
 direct measurement of inel with lower sys. unc.
 constraint on low mass diffraction cross-section
Experiment
inel (mb)
ALICE
(model)  2.6 (exp)
ATLAS
69.1  6.9 (model)  2.4 (exp)
CMS
68.0  4.0 (model)  3.1 (exp)
LHCb
66.9  4.4 (model)  2.9 (exp)
TOTEM
73.7  1.5 (model)  2.9 (exp)
SIF 2015 – 24/09/15
G. Latino – Risultati e Prospettive dell’Esperimento TOTEM
13/27

14. T , el and inel Measurement @ 7 TeV: Summary
LHCb
CMS
Very good agreement:
- among TOTEM measurement with different
methods (understanding of systematic
uncertainties and corrections)
- among LHC experiments
Experiment
Method
T (mb)
inel (mb)
el (mb)
Reference
ATLAS 2
95.35  1.36
71.3  0.9
24.0  0.6
Nucl. Phys. B 889 (2014), 486
TOTEM 1
99.1  4.3
73.7  3.4
25. 4  1.1
EPL 101 (2013), 21002
EPL 101 (2013), 21003 “
98.3  2.8
73.5  1.6
24.8  1.2
EPL 96 (2011), 21002
98.6  2.2
73.2  1.3
25.4  1.1
EPL 101(2013), 21002 3
98.0  2.5
72.9  1.5
25.1  1.1
EPL 101 (2013), 21004
14/27
SIF 2015 – 24/09/15
G. Latino – Risultati e Prospettive dell’Esperimento TOTEM

15. del/d|t| Measurement @ 8 TeV
* = 90 m data
Follow the same analysis
steps 7 TeV (optical functions basically the same):
Nel and (dNel/dt)|t=0 measurement
 T, el and inel with L-indep. method
* = 1000 m data
Preliminary studies towards
 measurement
β*(m)
RP approach (beam )
Lint (µb-1)
|t|- range (GeV2)
Elastic events
Reference 90
6 – 9.5 60
0.01 – 0.1
0.6M
PRL 111 (2013),
9.5
735
0.027 – 0.2
7.2M
Nucl. Phys. B899 (2015), 527
1000 3 20
6·10-4 – 0.2
0.4M
Analysis Ongoing
Possibility of  measurement
SIF 2015 – 24/09/15
G. Latino – Risultati e Prospettive dell’Esperimento TOTEM
15/27

16. (el / inel = Nel / Ninel)
T 8 TeV
new data available
at s = 2.76 TeV
T from
L –independent
Method
el and inel from
L - and -indepen.
el / inel ratio
(el / inel = Nel / Ninel)
PRL 111 (2013)
SIF 2015 – 24/09/15
G. Latino – Risultati e Prospettive dell’Esperimento TOTEM
16/27

17. del/d|t| Measurement @ 8 TeV with High Statistics
Nucl. Phys. B899, 527 (2015)
Nb = 1: B = b1 (Reference)
Nb = 2: B = b1 + b2t
Nb = 3: B = b1 + b2t + b3t2
High statistic data sample allowed a precise del/d|t| measurement (for < |t| < 0.2 GeV2)
“Purely” exponential slope excluded with a significance > 7 ( del/d|t| = Ae-B(t)|t|)
Quadratic and cubic polynomials in the exponent well describe data
Using the new parametrisations for extrapolation to t = 0 and applying the optical
theorem, new results for T are found in agreement with previous measurement:
Nb = 1 (previous, purely exponential)  T =  2.9 mb (with L-indep. method)
Nb = 2 (quadratic polynomial)  T =  2.1 mb
Nb = 3 (cubic polynomial)  T =  2.1 mb
17/27
SIF 2015 – 24/09/15
G. Latino – Risultati e Prospettive dell’Esperimento TOTEM

18. Elastic Scattering at Low |t|:  Measurement
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
=  /  [Telastic,nuclear(t = 0)]
Measurement of r by studying the Coulomb – Nuclear interference region down to
|t| ~ 610-4 GeV2
s = 8 TeV, with b* = 1000 m and RP approaching the beam ~ 3s
18/27
SIF 2015 – 24/09/15
G. Latino – Risultati e Prospettive dell’Esperimento TOTEM 18

19. Elastic Scattering in the Coulomb-Nuclear Interference Region
d/dt  |FC+H|2 = Coul. + Had. + Interf. 
TOTEM
Preliminary
Constrained by measured e-B(t)|t|
TOTEM Preliminary
Preliminary results on direct  8 TeV:
Indirect crude  7 TeV (from optical th.):
 |r| =  0.091
Analysis Ongoing
G. Latino – Risultati e Prospettive dell’Esperimento TOTEM
19/27
SIF 2015 – 24/09/15

20. G. Latino – Risultati e Prospettive dell’Esperimento TOTEM
dNch/d in 7 TeV
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
Previously unexplored forward  range
High “visible” fraction of inelastic cross section:
 95% inel
- Diffractive events with MDiff > 3.4 GeV/c2
- ND events > 99%
- EPL 98 (2012)
SIF 2015 – 24/09/15
G. Latino – Risultati e Prospettive dell’Esperimento TOTEM
20/27

21. dNch/d Measurement @ 8 TeV (I)
Combined analysis CMS (|| < 2.2) + TOTEM (5.3 < || < 6.4) on low-pileup run
of 8 TeV: common trigger (T2, bunch cross.), both experiments read out
Corrected down to PT = 0 MeV/c  direct comparison with MC
Three event samples: “Inclusive” (particles in any T2 arm, > 91% of inel);
“NSD-enh.” (particles in both T2 arms); “SD-enh.” (particles in only one T2 arm)
None MC event generator provides a consistent description of data
Inclusive
SD-enhanced
NSD-enhanced
First common paper with CMS: - Eur. Phys. J. C74 (2014)
SIF 2015 – 24/09/15
G. Latino – Risultati e Prospettive dell’Esperimento TOTEM
21/27

22. dNch/d Measurement @ 8 TeV (II)
Data sample with displaced interaction point
parasitical collision at β* = 90 m (2012, 8 TeV)
 ~11m  shifted  acceptance for T2
Measurement with -unc. uncertainty
Total uncertainty
Not possible to make reliable measurement in 6.9 <  < 6 due to large amount of material
- Eur. Phys. J. C75 (2015) 126 -
SIF 2015 – 24/09/15
G. Latino – Risultati e Prospettive dell’Esperimento TOTEM
22/27

23. Physics Programme for Run II
Stand-alone: repeat same physics s = 13 TeV
CMS+TOTEM: focus on central diffraction (CD) processes
- double arm proton detection: full reconstruction of initial state kinematics
- hermetic coverage for || < 6.5: initial vrs. final state comparison
- several physics processes of interest in hard and soft diffraction
- potentialities for the search for new physics  CD
(aka DPE)
Preliminary investigation of some physics channels in progress with the analysis of data from joint CMS-TOTEM high * run 8 TeV (2012)
The study/search for low cross section DPE processes requires running in high luminosity scenarios: capabilities of resolving event pile-up and multiple proton track reconstruction mandatory......
 upgrade programme needed
SIF 2015 – 24/09/15
G. Latino – Risultati e Prospettive dell’Esperimento TOTEM
23/27

24. Upgraded Roman Pot System
Existing RP220
(vertical + horizontal RPs)
Already installed in LHC tunnel during LS1
RP147 relocated to m
Two TDRs released:
 two complementary projects
SIF 2015 – 24/09/15
G. Latino – Risultati e Prospettive dell’Esperimento TOTEM
24/27

25. TOTEM Stand-alone Upgrade
Hit map for b* = 90 m
CERN-LHCC , TOTEM-TDR-002 (2014)
High * (90 m), special runs, low L
- Scientific objectives of DPE processes studies:
exclusive central diffraction;
low mass resonances and glueball states;
exclusive charmonium state;
search for missing mass and momentum candidates;
diffractive central jet production.
- CMS/TOTEM common data taking
- Lint  1 – 100 pb-1
- Only vertical RPs, with one (220-N) equipped with
diamond timing detectors (installed in 2015/16)
 TOF measurement on p (resolution of  50 ps)
gives information on Zv
- RPs at 214 m rotated by 8o  multi-track
capability (3D pixel Si detector under study for next upgrade)
- Possibility to reach moderate L with pile-up up to   1
SIF 2015 – 24/09/15
G. Latino – Risultati e Prospettive dell’Esperimento TOTEM
25/27

26. CMS-TOTEM Upgrade (CT-PPS)
CERN-LHCC , CMS-TDR-013, TOTEM-TDR-003 (2014)
CT-PPS: CMS-TOTEM
Precision Proton Spectrometer
Low * (0.5 m), standard runs, high L
- Scientific objectives of DPE processed studies:
EWK: LHC as a - collider
- measure   W+W-, e+e-, m+m-, t+t- ;
- search for AQGC with high sensitivity;
- search for SM forbidden ZZgg, gggg couplings…
QCD: LHC as a g-g collider
- exclusive 2 and 3-jets events, with M up to ~ GeV;
- inclusive 2 and 4-jets for g(x,Q2) and structure in pomeron;
- test of pQCD mechanisms of exclusive production;
- almost pure gluon jet samples…
BSM: search for new resonances and missing M
- clean events (no underlying pp event);
- JPC quantum numbers 0++, 2++
- CMS/TOTEM common data taking, Lint up to 100 fb-1
- CMS-TOTEM common R&D: detectors to be installed
in the relocated (tracking: 3D Si pixel det.) and newly
constructed (timing: quartz Cherenkov det.) horizontal RPs
Hit map for b* = 0.55 m
(low b* = standard at LHC)
SIF 2015 – 24/09/15
G. Latino – Risultati e Prospettive dell’Esperimento TOTEM
26/27

27. G. Latino – Risultati e Prospettive dell’Esperimento TOTEM
Summary & Outlook
TOTEM detectors fully commissioned and operative during LHC RunI
The analysis of collision data taken in special runs with different beam conditions (* = 3.5, 90, 1000 m, s = 7, 8 TeV) gave the measurements of:
- elastic scattering in a wide |t| range (6·10-4 < |t| < 3.5 GeV2)
- elastic, inelastic and total p-p cross-section
- evidence for non-exponential slope
- forward charged particle multiplicity (also in combination with CMS)
- forward DD and (ongoing) study of SD and DPE processes
Data taking with * = 1 km (s = 8 TeV): preliminary  measurement
First joint TOTEM/CMS data taking ( , s = 8 TeV) with common triggers and both experiments read out: analyses ongoing
LS-1 ( ): “consolidation” activities on detectors (electronics upgrade for DAQ and trigger integration with CMS, relocation of RP147)
After LS-1: repeat measurements at higher s;
RP upgrade with timing detectors: CERN-LHCC (TOTEM-TDR-002); diffraction together with CMS (common upgrade of forward proton detectors: CERN-LHCC (TOTEM-TDR-003 ; CMS-TDR-13)
Looking forward for new data taking during LHC Run II !!! 16
SIF 2015 – 24/09/15
G. Latino – Risultati e Prospettive dell’Esperimento TOTEM
27/27

28. Backup Slides

29. Elastic Scattering: from ISR to Tevatron
~1.4 GeV2
ISR
Diffractive minimum analogous
to Fraunhofer diffraction:
minimum moves to lower |t| with increasing s
 interaction region grows (as also seen from sT)
depth of minimum changes  shape of proton profile changes
depth of minimum differs between pp, pbarp  different mix of processes B1

30. Roman Pots (I)
Beampipes
Units installed into the beam vacuum chamber allowing to put proton detectors as close as possible to the beam
Protons at few rad angles detected down to  5 + d from beam (beam ~ 80m at RP)
 ‘Edgeless’ detectors to minimize d
Each RP station has 2 units, 5m apart.
Each unit has 3 insertions (‘pots’):
2 vertical and 1 horizontal
Horizontal Pot Vertical Pot BPM
Horizontal Pot: extend acceptance; overlap for relative alignment using common track
Absolute (w.r.t. beam) alignment from beam position monitor (BPM) B2

31. Roman Pots (II) Each Pot: 10 planes of Si detectors
200m thick
Roman Pots (II)
beam
Each Pot:
10 planes of Si detectors
512 strips at 45o orthogonal
Pitch: 66 m
Total ~ 5.1K channels
Digital readout (VFAT):
trigger/tracking
Hit Resolution:  ~ 10 m
Integration of traditional Voltage Terminating Structure with the Current Terminating Structure
Readout chip VFAT
Detectors expected to work
up to Lint ~ 1 fb-1
(no loss of performance during Run I)
Edgeless Si detector:
50 μm of dead area B3

32. Planar technology with CTS (Current Terminating Structure)
Si CTS Edgeless Detectors for Roman Pots
Planar technology with CTS
(Current Terminating Structure) I2 I1 + -
biasing ring Al p+ n+
cut edge
current
terminating
ring
SiO2
n-type bulk
50µm
Integration of traditional Voltage Terminating Structure with the Current Terminating Structure
bias gard/clean-up
ring (CR)
AC coupled microstrips made in planar
technology with novel guard-ring design
and biasing scheme
50 μm of dead area
50 µm B4

33. LHC Optics and TOTEM Running Scenarios
Acceptance for diffractive protons:
t  -p2 * 2: four-momentum transfer squared;  = p/p: fractional momentum loss
b* = 90 m
b* = 1000 m
b* = 0.55 m
> 1033 cm-2 s-1
~1027 cm-2 s-1
Diffraction:  > ~0.01 low cross-section processes (hard diffraction)
Elastic scattering: large |t|
Diffraction: all  if |t| > ~10-2 GeV2
Elastic scattering: low to mid |t|
Total Cross-Section
Elastic scattering: very low |t| Coulomb-Nuclear Interference
Total Cross-Section B5

34. Inelastic pile-up ~ 0.03 ev. / bx
Elastic pp Scattering: Hit Map in RPs
Coincidences of tracks reconstructed in left(45) and right(56) sectors:
two “diagonals” analyzed independently
Sector Sector 56
Sector 56
Sector 45
Aperture limitation, tmax
Beam
halo
β* = 3.5m (7σ) β* = 90m (10σ) β* = 90m (5σ)
x[mm] ty x
7 x1010 protons per bunch Inelastic pile-up ~ 0.8 ev. / bx
1.5 x1010 protons per bunch Inelastic pile-up ~ ev. / bx
6 x1010 protons per bunch
Inelastic pile-up ~ 0.03 ev. / bx
Hits associated to elastic scattering candidates B6

35. Optical Functions: Example at * = 90 m
L = (*)1/2 sin((s))
v = (/*)1/2 cos((s)) 
Idea:
Ly large Lx=0
vy = 0
y(220) = /2 x(220) = 
(parallel-to-point focussing on y)
(m)‏
hit distribution (elastic)
x = Lxx* + vxx* +D
y = Lyy* + vyy *
Optical functions:
- L (effective length)
- v (magnification)
defined by  (betatron function)
and  (phase advance);
- D (machine dispersion)
 describe the explicit path of particles through the magnetic elements as a function of the particle parameters at IP
 = p/p
(x*, y*): vertex position at IP
(x*,y*): emission angle at IP
t = tx + ty
ti ~ -(pi*)2 B7
G. Latino – TOTEM Physics Summary

36. * and  Resolution (* = 90 m)
Diffractive p
Elastic p
CERN-PH-EP B8

37. Roman Pot Alignment wrt Beam Centre: BLM
Collimator cuts a sharp beam edge symmetrically to the centre
RP approaches this edge until it scrapes …
… producing spike in BLM downstream
The second RP approaches
When both top and bottom pots “feel” the edge: they are at the same number of sigmas from the beam centre as the collimator and the beam centre is exactly in the middle between top and bottom pot B9 37

38. TOTEM Roman Pot Alignment Procedures
Critical procedures (fill-based): movable devices, beam optics variations
Pot position wrt LHC beam center:
alignment wrt collimators by approaching the beam “cut edge” (~ 20 mm)
Internal alignment of components within detector assembly:
metrology, local tracks (few mm)
Relative alignment of the pots in a station:
tracks in overlapping regions (Millepede algorithm, few mm)
Global alignment:
track based exploiting symmetries (co-linearity)
of hit profiles for elastically scattered protons,
also allows “left-right” constraints
(< 10 mm in x,  20 mm in y)
Bottom Pot
Top Pot
Flip
and shift
Final precision achieved:
~ 10(50) mm in x(y)  t/t ~ %
B10

39. TOTEM Elastic pp Scattering: Analysis (I)
Proton selection cuts
- collinearity cuts (left-right):
Θ*x,45 Θ*x,56
Θ*y,45 Θ*y,56
(width in agreement with beam divergence)
- low ξ cuts: |x*| < 0.6 mm and 2s cut in Dqy*
- vertex cuts (beam halo): |x*45 - x*56| < 27 µm
- optics related cuts
Collinearity in qy*
Missing acceptance in Qy*
Collinearity in qx*
Background subtraction
- interpolating the background tails (> 3 )
into the signal region (< 3 )
Acceptance correction
- assuming azimuthal symmetry
- correcting for smearing around
limitation edges
B11

40. TOTEM Elastic pp Scattering: Analysis (II)
Extrapolation limit
β*=90m
σ(Θ*)=1.7µrad
Unfolding of
resolution effects:
MC based iterative procedure
divergence
uncertainty
β*=3.5m
unfolding correction
Normalization (reconstruction efficiencies):
Trigger Efficiency (from zero-bias data stream) > 99.8% (68% CL)
DAQ Efficiency  %
Reconstruction Efficiency
– intrinsic detector inefficiency: – 3 % / pot
– elastic proton lost due to interaction: % / pot
– event lost due to overlap with beam halo (depends on RP position wrt beam and diagonals): – 8% (β*=90m); 30% (β*=3.5m)
Luminosity from CMS: systematic error of 4%
Systematic uncertainties: dominated by L and by analysis t-dependent effects
(misalignments, optics imperfections, energy offset, acceptance correction and un-smearing correction)
B12

41. del/d|t| Measurement @ 7 TeV
A = 506  23.0syst  0.9stat mb/GeV2
A = 504  26.7syst  1.5stat mb/GeV2
B = 19.9  0.27syst  0.03stat GeV-2
|t|dip= 0.53 GeV2
~ |t|-7.8
Analysis steps:
Alignment procedures/corr.
LHC optics calibration
Elastic candidate event sel.
Background subtraction
Acceptance correction
Unfolding of resolution effects
Normalization (recon. eff.)
Luminosity determination
System. uncertainties:
dominated by L and by analysis t-dependent effects
(energy offset, acceptance correction, misalignments, optics imperfections and un-smearing correction)
Integrated elastic cross-section: El = El, Meas. + El, Extr.
(L from CMS, with 4% unc.)
el = 25.4 ± 1.0lumi ± 0.3syst ± 0.03stat mb (91% directly measured)
el = 24.8 ± 1.0lumi ± 0.7syst ± 0.2stat mb (67% directly measured)
B13

42. Elastic Scattering at low |t|: Systematic Errors
Individual contributions to errors:
analysis t-dependent:
– misalignments
– optics imperfections
– energy offset
– acceptance correction
– unsmearing correction
analysis normalization:
– event tagging
– background subtraction
– detector efficiency
– reconstruction efficiency
– trigger efficiency
– “pile-up” correction
Luminosity from CMS ( 4%)
Constant slope for
0.005 < |t| < 0.2 GeV2
Mario Deile –
B14

43. 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)
B15

44. Dependence of Nuclear Slope B on Energy

45. Inelastic Cross Section Measurement @ 7 TeV
All LHC experiments performed direct measurement: inel = Ninel /L
General analysis steps for the measurement
Corrections to the “visible” inel in the given kinematic acceptance region
trigger and event reconstruction efficiency, background rejection and pile-up
(experimental uncertainty dominated by uncertainty on L)
Corrections for “missing” inel
events lost due to (eventually) limited acceptance in central region,
events lost due limited acceptance in forward region, related to
low mass diffraction  leading contribution (and uncertainty)
Experiment
Acceptance  range
“Visible”  range
MX range (GeV/c2)
Reference
ALICE
- 3.7 <  < 5.1
 > 510-6
MX > 15.7
EPJ C73 (2013), 2456
ATLAS
2.09 < || < 3.84
Nat. Commun. 2 (2011), 463
CMS
3 < || < 5
Phys. Lett. B 722 (2013), 5
LHCb
2 <  < 4.5
 >  1.510-6 (n)
MX >  8.6 (n)
arXiv: (2014)
TOTEM
3.1 < || < 6.5
 > 2.410-7
MX > 3.4
EPL 101 (2013), 21003
B17

46. Inelastic Cross Section @ 7 TeV: TOTEM
Direct T1 and T2 measurement: inel = Ninel /L (L from CMS)
Data sample
- Oct run with β* = 90 m:
same data subsets used for the L-independent
total cross section measurement
- T2 triggered events
- Low pile-up: (μ = 0.03) T2 η
tracks
Inelastic events in T2: classification
- Tracks in both hemispheres: mainly non-Diffractive
minimum bias (ND) and Double Diffraction (DD)
- Tracks in a single hemisphere: mainly single
diffraction (SD) with MX > 3.4 GeV/c2
 Optimized study of trigger efficiency and
beam gas background corrections
B18

47. inel @ 7 TeV: TOTEM (Corrections)
Corrections to the “T2 visible” events ( 95%)
- Trigger Efficiency (from zero bias data, vs track multiplicity):  0.7 %
- Track reconstruction efficiency (based on MC tuned with data): 1.0  0.5 %
- Beam-gas background (from non colliding bunch data):  0.4 %
- Pile-up (μ = 0.03) (from zero bias data):  0.4 %
Corrections for “missing” inelastic cross-section
- Events visible in T1 but not in T2 (from zero bias data):  0.4 %
- Rapidity gap in T2 (from T1 gap probability transferred to T2):  0.15 %
- Central Diffraction: T1 & T2 empty (based on MC):  0.35 %
- Low Mass Diffraction (based on QGSJET-II-03 MC): 4.2 %  2.1 %
(constrained by elastic scattering measurement, see later)
Uncertainty related to L (CMS): 4%
Compatible with other similar
LHC
σinelastic = 73.7 ± 0.1stat ± 1.7syst ± 3.0lumi mb
- EPL 101 (2013)
B19

48. Low-Mass Diffraction: T1+T2 Acceptance
QGSJET-II-03:
dN/dMdiff
MX > 3.4 GeV/c2 (T2 acceptance)
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
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
B20

49. Low-Mass Diffraction: Constraint from Nel
Constraint on low mass diffraction cross-section from TOTEM data:
Use total cross-section determined from
elastic observables (via the Optical Theorem)
 no assumption on low mass diffraction
sinel = stot – sel = 73.2  1.3 mb
and the measured “visible” inelastic cross-section for |h| < 6.5 (T1, T2)
sinel, |h| < 6.5 = 70.5  2.9 mb
to obtain the low-mass diffractive cross-section
(|h| > 6.5 or MX < 3.4 GeV/c2)
sinel, |h| > 6.5 = sinel - sinel, |h| < 6.5 = 2.6  2.2 mb
(or < % CL) [MC: 3.1  1.5 mb]
- EPL 101 (2013)
B21

50. Elastic Scattering in the Coulomb-Nuclear Interference Region
Experimental data Physics parameters (, …)
Theoretical/phenomenological models
Comparison
Modulus constrained by measurement: ds/dt  A e-B(t) |t| B(t) = b0 + b1 t + …
Phase argFH (interference term): very little guidance by data
(QED)
Simplified West-Yennie formula:
constant slope B(t) = b0
constant hadronic phase arg(FH) = p0 (“costant phase”)
Y(t) acts as real interference phase:
General Kundrát-Lokajíček formula:
any slope B(t)
any hadronic phase:
if argFH(t)  “peripheral phase”
if argFH  cost  “central phase”
complex Y(t):
B22

51. Elastic Scattering in the Coulomb-Nuclear Interference Region
data sensitivity region ? ? ?
“central phase”:
“constant phase”:
“peripheral phase”:
Only 1 free parameter: p0 = (0) 
B23

52. Further Measurements (TOTEM)
Absolute luminosity measurement 7 TeV):
The “luminosity-independent” method
also yields the luminosity calibration
June 2011: Lint = (1.65  0.07) mb [CMS: (1.65  0.07) mb-1] October 2011: Lint = (83.7  3.2) mb [CMS: (82.0  3.3) mb-1]
Excellent agreement with CMS L measurement
Luminosity- and ρ-independent ratios:
B24

53. importance of the dN/dh measurement
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 (14) TeV pp collisions at LHC correspond to
pCR-pAIR collisions with pCR of ~ 25 (100) PeV
B25

54. Big Challenge: Secondary Particles in T2
Track reconstruction in T2 is challenging because of the large amount of charged particles generated by the interaction of primaries with the material placed between the IP and T2
90% (80% ) of the signal (tracks) in T2 is given by secondaries
A detailed revision of the volumes and of the GEANT setting was necessary HF IP
T2 telescope HF
Effect of the BP on the hit didtribution
Material contributing to secondary
particle generation:
- BP flange and ion-pumps
- BP cone at h=5.53
- lower edge of HF
B26

55. Charged Particle Pseudo-Rapidity Density (dNch/d) @ 7 TeV
T2 alignment
- Internal alignment
two different track-based methods (HIP
and Millepede) implemented in order to
resolve misalignment (x-, y-shifts) among
detectors in a quarter
- Quarter-quarter alignment
using tracks in the overlap region
- Global alignment
each arm aligned (shifts and tilts) respect
to the nominal position by imposing the
symmetry of the “beam pipe shadow”
on each detector plane z IP x
Final precision achieved:
~ 1 mm (x-,y-shifts); ~ 0.4 mrad (xz-, yz-tilts)
B27

56. dNch/d in T2: Analysis Highlights
Data sample (2011):
events at low luminosity and low pile-up, triggered with T2 (5.3 < || < 6.5)
Selection:
at least one track reconstructed in T2
Primary particle definition:
charged particle with t > 0.310-10 s, pT > 40 MeV/c
Primary particle selection:
-primary/secondary discrimination, data-driven
based on reconstructed track parameters (ZImpact)
Primary track reconstruction efficiency:
- evaluated by MC as a function of track  and hit multiplicity in T2 quarter
- average efficiency of  80%
- fraction of primary tracks within the selection cuts of 75% – 90% ( dependent)
Un-folding of () resolution effects:
MC driven bin “migration” corrections
Systematic uncertainties (< 10%):
dominated by primary track efficiency and global alignment correction uncertainty
primary
secondary
B28

57. Soft Double Diffraction @ s = 7 TeV
Both protons break up  2 diffractive masses M1, M2
Central rapidity gap
-|h|min,2
|h|min,1
Ultimate goal: 2-dim. cross-section
h = 4.7
h = 6.5
Difficulties:
no leading protons to tag
for large masses ( small
central gap) not easy to
separate from non-diffractive
events
First step: sub-range with particles triggering both T2 harms, veto on T1
4.7 < ||min,1/2 < or GeV < M1/2 < 8 GeV
ND back. estimate: scaling MC prediction using ND-dominated data sample (“2T1+2T2”)
SD back. estimate: using SD-dominated data sample (“0T1+1T2”) with p in RP
 Event selection with high DD purity ( 70%)
B29

58. Soft Double Diffraction: Results @ 7 TeV
Partial 2-dim. cross-section in 2 x 2 bins:
Sum: 2 2 1 1
- PRL 111 (2013)
Leading systematics:
- missing DD events with unseen particles generated at h < hmin
- backgrounds from non-diffractive, single diffractive, central diffractive events
So far, only a small part of DD measured: 116 b out of ~5 mb, but:
benchmark for Monte Carlos:
Pythia 8:
Phojet:
Improvement expected with 8 TeV data:
also CMS detector information available (joint run)
B30