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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 - PowerPoint PPT Presentation
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2012 LHC Days in Split, Croatia
Karsten Eggert (CWRU)
on behalf of the TOTEM collaboration
Elastic scattering
Total Cross-section
Inelastic cross-section
Particle Production
Diffraction
Runs with CMS
Future runs
Perspectives after the shut-down
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
TOTEM Results and Perspectives
Karsten Eggert– p. 1
jet
jet
b
TOTEM Physics OverviewTOTEM Physics Overview
Total cross-section
Elastic Scattering
Cosmic Ray Physics
Diffraction: soft and hard
Karsten Eggert– p. 2
IP5
RP147 RP220
24 Roman Pots in the LHC tunnel on both sides of IP5 measure elastic & diffractive protons close to outgoing beam
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
TOTEM Detectors (T1, T2 and RP) on both sides of IP5
Karsten Eggert– p. 3
p. 4Karsten Eggert–
T1(CSCs)
Detectors
Vertical Pot
Vertical Pot
Vertical Pot
Vertical Pot
Horizontal Pots
RP 147 Package of 10 “edgeless” Si-detectors
T2(GEMs)
The Roman Pot System at 220 m
Karsten Eggert– p. 5
ydet
y*
IP5
y*
RP220220m
beam axis
scattered protonbeam-optical elements (magnets)
(x*, y*): vertex position
(x*, y
*): emission angle: t pxy
= p/p: momentum loss (diffraction)
Design considerations:
Two independent detection systems with 5 m lever arm redundant trigger scenarios
10 Silicon detectors / RP ~ 10 m precision
Reliable track reconstruction in both projections 5 planes / projection
Determine the proton angle in both projections ~ 2 rad precision
Approach the beam as close as possible to ~ 5 – 10 beam width
Space for adding detectors for future upgrades !!!
Beam width @ vertex Angular beam divergence Min. reachable |t|
Standard optics * ~ 1 m x,y* small x,y
*) large |tmin| ~ 0.3–1 GeV2
Special optics * = 90 m x,y* large x,y
*) small |tmin| < 10 GeV2
**, yx *
22
min
p
nt Optimized optics
Proton position at a given RP (x, y) is a function of position (x*, y*) and angle (x*, y
*) at IP5:
Scattering angle reconstructed in both projections
Excellent optics understanding required
Δμ(s)β(s)βL(s) * sin
Elastic proton kinematics reconstruction (simplified):
The effective length and magnification expressed with the phase advance:
Δμ(s)β(s)βυ(s) * cos1 s
(s')ds'βΔμ(s)0
1
RP IP5
measured
in Roman
Potsreconstructed
Proton transport matrix
0 ,
/
/
**
*,
*
pp
LyvydsdL
xds
dv
yyRPy
xxRPxx
Karsten Eggert– p. 6
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 m step produces a spike in a Beam Loss Monitor downstream of the RP
The RP – beam contacts are also registered as spikes in the trigger rate
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
Karsten Eggert– p. 7
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
Elastic pp scattering : proton reconstruction
Two diagonals analysed independently
t = -p2
p/p
Sec
tor
45
Sec
tor 5
6
Sector 56
Sector 45
Sector 56
Aperture limitation, tmax Beam
halo
=3.5m (7) =90m (10) =90m (5)
Elastic pp scattering: topology (hit map in RP detectors)
x[mm] x[mm]
y[
mm
]
y[
mm
]
Karsten Eggert– p. 8
Width in agreement with beam divergence of 17 rad x is measured with 5m lever arm spectrometer
Low , i.e. |x| < 0.4 mm and 2 cut in y*
Collinearity in x*Collinearity in y
*
Elastic Scattering: Collinearity
Missing acceptance in θy*
Beam di
verg
ence
|ty | (diagonal 2)
|ty | (diagonal 1)
Scattering angle on one side versus the opposite side
Karsten Eggert– p. 9
Collinearity cut (left-right)
*x,45
↔*x,56
*y,45
↔*y,56
Elastic pp scattering : analysis
Background subtraction
Acceptance
correction
Karsten Eggert– p. 10
First measurement of the elastic pp differential cross-section
First published data in 2011
EPL 95 (2011) 41001
EPL 96 (2011) 21002
Karsten Eggert– p. 11
2011 with * = 3.5 m
Comparison to some models
B (t=-0.4 GeV2)
tDIP
t-n [1.5–2.5 GeV2]
20.2 0.60 5.023.3 0.51 7.0
22.0 0.54 8.4
25.3 0.48 10.420.1 0.72 4.2
23.6 ± 0.5 0.53 ± 0.01 7.8 ± 0.3
Better statistics at large t needed (in progress)Karsten Eggert– p. 12
None of the models really fit
p. 13Karsten 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
||el / tBeAdtd
|t|dip= 0.53 GeV2
~ |t|7.8
Elastic pp Scattering at 7 TeV: Differential Cross-Sectiont range : 710-3 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)
Integrated elastic cross-section:Additional data set under analysis:
2 GeV2 < |t| < 3.5 GeV2
Low t - distribution
p. 14Karsten Eggert–
Constant slope for
0.007 < t < 0.2 GeV2
Individual errors
Karsten Eggert– p. 15
Slope parameter B and elastic cross-section
B constant in the range 0.007 < t < 0.2 GeV2
B increases with energy
el / tot increases with energy
~1.4 GeV2
Diffractive minimum: analogous to Fraunhofer diffraction: |t|~ p2 2
• exponential slope B at low |t| increases
• minimum moves to lower |t| with increasing s
interaction region grows (as also seen from tot)
• depth of minimum changes shape of proton profile changes• depth of minimum differs between pp, pˉp different mix of processes
ISR
Elastic scattering – from ISR to Tevatron
7 TeV
Karsten Eggert– p. 16
p. 17Karsten Eggert–
Elastic Scattering and Total Cross-Section at 8 TeV
July 2012: runs at * = 90 m
only RP alignment, RPs moving
collinearity, low , common vertex
Elastic Scattering and Total Cross-Section at 8 TeV
July 2012: runs at * = 90 m
only RP alignment, RPs moving
Preliminary t-distributions (unnormalised)
larger |t|:
• possible at *=0.6m
• difficult due to 2xSDand other background
down to |t| ~ 6 x 10:
foreseen at * = 1km
p. 18Karsten Eggert–
TOTE
Mpr
elim
inar
y TOTE
Mpr
elim
inar
y
Total Inelastic Cross Section Measurement at √s = 7 TeV
All TOTEM detectors are used
Karsten Eggert– p. 19
1. based only on elastic scattering via optical theorem
2. 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
Karsten Eggert–
20
Direct measurement of the Inelastic Cross-Section at √s=7 TeV
T1: 3.1 < < 4.7
T2: 5.3 < < 6.5
T2
η
tracks
T2
η
η
Inelastic events in T2: classification
tracks in both hemispheresnon-diffractive minimum bias
double diffraction
tracks in a single hemisphere
mainly single diffraction
MX > 3.4 GeV/c2
Corrections to the T2 visible events
σinelastic, T2 visible = 69.7 ± 0.1 (stat) ± 0.7 (syst) ± 2.8 (lumi) mbKarsten Eggert– p. 21
σinelastic, T2 visible σinelastic
Missing inelastic cross-section
σinelastic = 73.7 ±0.1(stat) ±1.7(syst) ±2.9(lumi) mb
Karsten Eggert– p. 22
23
MX>3.4 GeV/c2 (T2 acceptance)
S
D d S
D/d
SIBYLL/PYTHIA8
QGSJET-II-4
low mass contribution
S. Ostapchenko
arXiv:1103.5684v2 [hep-ph]
Inelastic Cross Section : low mass diffraction
Correction based on QGSJET-II-4
Mx < 3.4 GeV = 2.7 ± 1.5 mb
Karsten Eggert–
By comparison with the measured inelastic cross-section (using the total cross-section)
the low mass single diffraction can be determined:
tot – 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
tot = (98.0 ± 2.5) mb
p. 24Karsten Eggert–
3 Ways to the Total Cross-Section
Excellent agreement between cross-section measurements at 7 TeV using
- runs with different bunch intensities,
- different methods.
(ρ=0.14 [COMPETE])
different bunch intensities !
June 2011 (EPL96): tot = (98.3 ±2.8) mb
Oct. 2011 (PH pre.): tot = (98.6 ±2.2) mb
tot = (99.1 ± 4.3) mb
p. 25Karsten Eggert–
Cross-sections with different methods
COMPETE extrapolation: = 0.141 0.007
done before TOTEM measurement
Luminosity determination and ratios
Luminosity calibration:
1) L= 82/b ± 4% L= 83.7/b ± 3.8%
2) L= 1.65/b ± 4% L= 1.65/b ± 4.5 %
Luminosity and ρ independent ratios:
σel/ σtot = 0.257 ± 2% σel/ σinel=0.354 ± 2.6%
Estimated by CMS Estimated by TOTEM
Summary:
The cross-section measurements are in excellent agreement using:
runs with different bunch luminosities
different methods
Karsten Eggert– p. 26
p. 27Karsten Eggert–
A First, Very Crude Estimate at 7 TeV
056.0009.01
dd
162
inelel
0
el
int2
NN
tN
tL
(95% CL),or, using Bayes’ approach (with uniform prior || distribution):
= 0.145 0.091 [COMPETE extrapolation: = 0.141 0.007]
= 0
.135
± 0
.044
TO
TE
M, 7
TeV
Not so exciting, but …
From optical theorem:
)0(Im
)0(Re
tT
tT
p. 28Karsten Eggert–
22 4
2
2/ 2
2 2
2
d
dt
4
1
16
B ttot
tot B t
c G t
t
G te
t
ec
Measurement: Elastic Scattering at Low |t|
Optical Theorem: ,
4( 0)tot elastic nuclearT t
s
= fine structure constant = relative Coulomb-nuclear phaseG(t) = nucleon el.-mag. form factor = (1 + |t| / 0.71)-2
= / [Telastic,nuclear(t = 0)]
Total (Coulomb & nuclear)
Nuclear scattering
Coulomb-Nuclear interference
Coulomb scattering dominant
Measurement of by studying the Coulomb – Nuclear interference region down to
|t| ~ 6 x 10-4 GeV2
Reachable with * ~ 1000 m still in 2012 if RPs can approach beam centre to ~ 4
How to reach the Coulomb-Nuclear Interference Region ?
p. 29Karsten Eggert–
RP window position
(real for n=2m rad)
RP approach the beam to ~ 4 Beam emittance n < 2 m rad
Challenging but possible
push * to > 2000 m
good t-resolution needs parallel-to-point focussing
in both x and y (phase advance /2)
Additional magnet cables needed. To be installed during LS1
√s = 8 TeV √s = 13 TeV
p. 30Karsten Eggert–
The * = 1000 m Optics
• special beam optics with * = 1000 m fully commissioned
• collisions in IP1 and IP5 found
• vertical emittances n ~ 2 m rad
• 4 vertical TOTEM RPs (out of 8) aligned at ~4 • time slot ended no physics data taken yet, diagnostic data on halo background being analysed
Physics run scheduled for October 2012
MD in June: first unsqueeze to 1km achieved
14 September:
Karsten Eggert–
31
Perspectives on Diffractive Physics, e.g. Double Pomeron Exchange
CMSTOTEM
MPP2 = 1 2s
-ln 2
Rapidity Gap
-ln 1
Scattered proton
Scattered proton
β* = 90m optics runs: DPE protons of -t > 0.02GeV2 detected by RP nearly complete ξ-acceptance
σDPE measurement method:
21
2
0 0
21
2,121
221)(
dtdt
ddtdt
eeCdtdt
d
DPEDPE
BtBtDPE
p. 32Karsten Eggert–
Correlation between the forward proton(s) and particles in T2
DP
SD
(low )
Karsten Eggert–
33
Single diffraction large
Rapidity Gap
= -ln
MX
2 = s
Single diffraction large
p. 34Karsten Eggert–
Diffractive Analyses Ongoing
Based on * = 90 m (7 TeV) run in Oct. 2011 (RP @ 4.8 – 6.5):
• Central Diffraction (d2DPE / dt1 dt2, DPE )
• Single Diffraction (dSD/dt , dSD/d , SD )
• Double Diffraction Select diff. masses 3.4 GeV < M < 10 GeV requiring tracks in both T2s, veto on T1s
Extend studies over full range with CMS (2012 data)
T1 T1 T2T2
p. 35Karsten Eggert–
Charged Particle Pseudorapidity Density dN / d
T2[T1]
Analyses in progress:
• T1 measurement at 7 TeV (3.1 < < 4.7)• NEW: combined analysis CMS + TOTEM (0 < < 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 * = 90 m (7 July 2012)
vertex at ~11m shifted acceptance:
EPL 98 (2012) 31002
Joint Data Taking with CMS
p. 36Karsten Eggert–
Realisation of common running much earlier than ever anticipated
1.Hardware: electrical from RP220 to CMS trigger within CMS latency
2.Trigger: bi-directional level-1 exchange same events taken
3.Synchronisation: orbit number and bunch number in data streams
4.Offline:- common repository for independently reconstructed data- merging procedure common n-tuples
Joint Data Taking with CMS
p. 37Karsten Eggert–
Abundant material for analysis activities throughout LS1
Analyses starting:
• hard diffraction: p + dijets (90m runs)
• combined dNch / d and multiplicity correlations
Date, Set Trigger Inelasticevents
RPposition
July 7, DS 2 T2 || RP2arms || BX ~2 M 6
July 12-13, DS 3a T2 || RP2arms || BX ~10 M 9.5 V, 11 H
July 12-13, DS 3b T2 || RP2arms || CMS(CMS = 2 jets @ pT > 20GeV, 2 , 2 central e/
~3.5 M 9.5 V, 11 H
tot, inel with CMS,
soft & semi-hard diffraction,
correlations
Date Trigger Inelasticevents
May 1 T2 || BX ~5 M no RP
dN/d,
correlations,
underlying event
May 2012: low pileup run: * = 0.6 m, s = 8 TeV, T1 & T2 & CMS read out
July 2012: * = 90 m, s = 8 TeV, RP & T1 & T2 & CMS read out
Runs Planned for 2012 / 2013
p. 38Karsten Eggert–
• * = 1000 m: scheduled for 24 October study interference region, measure
• RP insertions in normal physics runs (* = 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 (~ 5 %) with RPs at * = 0.6 m (in May RPs were not aligned) study soft central diffraction final states with 2 leading protons defining Pomeron-Pomeron mass M2 = s good resolution at * = 0.6 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)
p. 39Karsten 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 with *=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
The End
p. 40Karsten Eggert–