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Frigyes Nemes (Eötvös University)
on behalf of the TOTEM collaboration
http://totem.web.cern.ch/Totem/
Hadron Structure'13
2013, 29 June – 4 July
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 1
TOTEM Physics Total cross-section
Elastic Scattering
jet
jet
Diffraction: soft (and hard with CMS)
b
Forward physics
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 2
IP5
Experimental layout
T1: 3.1 < h < 4.7
T2: 5.3 < h < 6.5
T1 T2 CASTOR (CMS) 10 m
14 m
3 Frigyes Nemes, TOTEM
RP147 RP220
m m
m
IP5
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 3
The inelastic telescope T1 Properties:
• installed inside CMS at 7.5 to 10.5 m from IP5
• there is one telescope on each side of IP5
• each telescope consists of two quarters
• the quarters are formed by 5 equally spaced planes
• the planes contain 3 trapezoidal CSC detectors, each covering 60 ̐ in azimuth
• Cathode Strip Chamber: gaseous detector with 3 read-out coordinates (at 60 ̐ wrt. each other)
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 4
The T2 inelastic telescope Properties:
• installed inside CMS shielding between HF and Castor calorimeters
• centered around 13.5 m from IP5
• there is one telescope on each side of IP5
• each telescope contains two quarters
• each quarter formed by 10 semi-circular planes, assembled in 5 back-to-back mounted pairs
• each plane equipped with a Gas Electron Multiplier detector
• gaseous detector, electron multiplication by 3 perforated foils (2 mm separation)
• radial segmentation: strips (resolution ≈ 0.15 mm)
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 5
Roman Pot stations
Horizontal RP
RP unit: 2 vertical, 1 horizontal pot + BPM
BPM Vertical RPs
6 1 Roman Pot 10 planes of edgeless detectors
3.5 cm
Si edgeless detector
1 RP station:
• 2 units at about 5 m distance
• measurement of very small proton
scattering angles (few µrad)
• vertical and horizontal pots mounted as
close as possible to the beam
• BPM fixed to the structure gives precise
position relative to the beam
• overlapping detectors: relative alignment
(10 µm inside unit between 3 RPs)
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 6
Essential for TOTEM physics !
• The relevant magnet lattice:
Proton transport description IP5 → Roman Pots
• Proton position at a given RP (x, y) is a function of (x*, y*) and angle (Qx*, Qy
*) at IP5
Machine imperfections alter the optics:
• Strength conversion error, σ(B)/B ≈ 10-3
• Beam momentum offset, σ(p)/p ≈ 10-3
• Magnet rotations, beam harmonics, …
LHC Optics
RP IP5
Measured… … and reconstructed proton kinematics
Perturbed element δLy,b1/Ly,b1 [%]
MQXA.1R5 0.98
MQXB.A2R5 −2.24
y
*
yL
yΘ
*
1
xds
dΘ
ds
dLΘ x
xx*
x
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 7
Optics estimation based on:
• MAD-X based Monte-Carlo
• Measured optical function ratios from Roman Pots
Optics optimization
Spread due to imperfections
Optimized
F. Nemes, H. Niewiadomski, LHC Optics Determination with Proton Tracks
IPAC'12, Louisiana, USA, 20-25.05.2012
Measurement MAD-X Matching
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 8
Physics results
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 9
Elastic scattering Elastic tagging:
• s = 7 TeV, β* = 3.5 m
• Topology, collinearity cuts
Collinearity Θx
Spread in agreement with beam divergence (17-18 μrad)
Collinearity Θy
[EPL 95 (2011) 41001]
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 10
TOTEM first elastic dσ/dt result After acceptance corrections, unfolding, inefficiency corrections, luminosity:
• |t| range spans from 0.36 to 2.5 GeV2
• below |t| = 0.47 GeV2 exponential e-B|t| behavior
• dip moves to lower |t|, proton becomes “larger“
• 1.5 - 2.0 GeV2 : power low behavior |t|-n
pp elastic dσ/dt
@ISR
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 11
Several model descriptions: • the data show a strong discriminative power
Bourrely model & Petrov model: • the slope B|t|=0.4 GeV2 , tdip and the exponent n at
large |t| are consistent with the data • not consistent with the cross-section dσ/dt in the
measured range • other models are less consistent
Model predictions & fits
The measured dσ/dt compared with
predictions of several models
B
(t=-0.4 GeV2)
[GeV-2]
tDIP
[GeV2]
t-N [1.5–2.0 GeV2]
[N]
Islam 19.9 0.65 5.0
Jenkovsky 20.1 0.72 4.2
Petrov 22.7 0.52 7.0
Bourrely 21.7 0.54 8.4
Block 24.4 0.48 10.4
TOTEM 23.6 ± 0.5 ± 0.4 0.53 ± 0.01 ± 0.01 7.8 ± 0.3 ± 0.1
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 12
Low-t measurement, cross-sections Properties: • β* = 90 m
• excellent agreement between the two measurements with different optics
• The exponential slope B confirms that it increases with √s:
• Extrapolation to t = 0:
• Integral elastic cross-section:
• Total cross-section (with optical theorem):
1
16
0
2
2
2
t
eltot
dt
dc
-2GeV 3.02.01.20 syststatB
2-
syststat
0
GeV mb )7.265.17.503( tdt
d
mb 2.12.08.24mb 5.16mb 3.8 measuredextrapol.
syststatel
mb 8.22.03.98 syststattot
mb 6.05.733.1
8.1
syststateltotinel
01.0
08.014.0
EPL 96 (2011) 21002
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 13
|tmin| = 5 · 10-3 GeV2 at 7 TeV
RP@ 10 σbeam s ize@RP
(RP @ 6.5, 5.5, 4.8 σbeam size@RP )
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 14
EPL 101(2013) 21002
Extrapolation to t = 0 • Slope parameter:
• Extrapolation:
• Elastic cross section:
• 91 % is measured
• EPL 101(2013) 21002
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 15
-2GeV 27.003.089.19 syststatB
2-
syststat
0
GeV mb )239.04.506( tdt
d
mb 07.103.043.25 syststatel
Trigger: at least one track in T2
• 95 % of inelastic events
1. Raw rate: event counting with T2 Experimental corrections: trigger and reconstruction inefficiencies, beam-gas event suppression, pile-up
2. Visible rate: visible with T2 in perfect conditions Estimation of events with no tracks in T2: T1-only events, events with gap over T2, low-mass diffraction
3. Physics rate: true rate of inelastic events
• only one major Monte-Carlo-based correction: low-mass diffraction (which can be constrained from data)
Inelastic cross-section measurement
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 16
EPL 101 (2013) 21003
inel = 73.7 ± 3.4 mb
σtot with 4 methods At s=7 TeV:
1. Low luminosity (CMS) + Elastic d/dt + Optical th. ( EPL 96(2011) 21002 )
depends on CMS luminosity for low-L bunches, elastic efficiencies and on ρ
2. High luminosity (CMS) + Elastic + Optical theorem (EPL 101 (2013) 21002)
3. High luminosity (CMS) + Elastic + Inelastic (EPL, 101 (2013) 21004)
minimizes dependence on elastic efficiencies and no dependence on ρ
4. Elastic ratios + Inelastic ratios + Optical theorem (EPL, 101 (2013) 21004)
Eliminates dependence on luminosity
tot = 98.3 ± 2.8 mb
tot = 98.6 ± 2.2 mb
tot = 99.1 ± 4.3 mb
tot = 98.0 ± 2.5 mb
1
16
0
2
2
2
t
eltot
dt
dc
ineleltot
INELEL
t
EL
totNN
dt
dN
c
0
2
2
1
16
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 17
Luminosity independent cross-sections s=8 TeV • β* = 90 m
• CERN preprint: CERN-PH-EP-2012-354
• Accepted by PRL
• Elastic, inelastic, total cross-sections
σtot
[mb]
σel
[mb]
σinel
[mb]
101.7 ± 2.9 27.1 ± 1.4 74.7 ± 1.7
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 18
Hadronic-Coulomb interference at 8 TeV Analysis aim:
• Measure dσel/dt at the smallest possible proton |t| (where the Coulomb interaction can be probed):
• Coulomb + Hadronic + Interference
• Determination of ρ:
• Further improve the total cross-section σtot measurement
The relevant data set:
• s = 8 TeV, β* = 1000 m
• RP at 3 σbeam
• |t|min = 6 10-4 GeV2
TOTEM Preliminary
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 19
0Im
Re
t
H
H
A
A
2
HCAdt
d
Hadronic-Coulomb interference at 8 TeV Extraction of ρ and σtot by fitting the
Hadronic-Coulomb interference region:
Error bars include:
• Fit statistical uncertainty
• The effect induced on the fit by the relevant experimental uncertainties (misalignment, normalization,..)
Green line + band: 8 TeV σtot
measurement (β* =90m, luminosity independent):
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 20
model009.0
009.0010.0027.0107.0
syststat
Forward and diffractive physics
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 21
25 mb
10 mb
5 mb
1 mb
M
M Double Pomeron
Exchange
Double Diffraction
Single Diffraction
Elastic Scattering
60 mb
<< 1 mb
Inelastic and Diffractive Processes A
ll th
e d
raw
ings
sh
ow
so
ft in
tera
ctio
ns.
In
cas
e o
f h
ard
inte
ract
ion
s th
ere
sho
uld
be
jets
, w
hic
h fa
ll in
th
e sa
me
rap
idit
y in
terv
als
.
M
ea
sure
(M
,,t)
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 22
dNch /dη measured with T2, s=7 TeV Very forward measurement with T2 :
• Published EPL, 98 (2012) 31002
• Visible cross section measured on data: ~ 94% σinel
• Diffractive mass Mdiff > 3.4 GeV
• Main contributions to the systematical error:
• Subtraction of secondary particles.
• Track efficiency
• Misalignment uncertainties
dN
ch/d
h
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 23
Combined with other LHC exp.
CMS+TOTEM common dNch /dη @ 8 TeV Very forward measurement with T2 :
• CMS vertex information is used to reduce the pile-up correction
• Both CMS and TOTEM analysis obtained triggering with T2, on the same events
• Same CMS-TOTEM event selection (at least a track reconstructed in T2)
• Measurements are representative for an inelastic event sample with at least a primary charged particle with pt >40 MeV/c produced in the range 5.3 < |η| < 6.5
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 24
Diffractive physics
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 25
Soft Single Diffractive cross-section 7 TeV Low mass diffraction ( 2 · 10-7 < ξ < 10-6 )
• Tracks in the T2 hemisphere opposite to the proton
Very high mass ( ξ > 2.5 % )
• SD events are triggered with T2, only 1 proton required in RP
• M obtained from the rapidity gap estimation based on charged track η in T1 and T2 Δη= - ln(M2/s). This allows a better ξ resolution (σ(ξ)/ξ ~ 1) for low medium mass
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 26
MX2 = s
Rapidity Gap
Dh = -ln
h
RP RPT2 T2
IPsector 45 sector 56
=Dp/p h
RP RPT2 T2
IPsector 45 sector 56
h
MX2 = s
Rapidity Gap
Dh = -ln
7
7
Soft Single Diffractive cross-section 7 TeV
Corrections included:
• Trigger efficiency
• Reconstruction efficiency
• Proton acceptance
• Background subtraction
• Extrapolation to t = 0
Missing corrections:
• ξ – resolution
• Beam divergence effects
Estimated uncertainty:
• B ~ 15 %, σ ~ 20 %
Very preliminary result:
• σSD = 6.5 ± 1.3 mb
• 3.4 < MSD < 1100 GeV
• Very-high masses: ongoing
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 27
teCdt
d B
Soft Double Diffractive cross-section at 7 TeV
Event selection:
• Trigger with T2, at least one track in both T2 hemispheres , no tracks in T1
• “(0T1+2T2) topology”
Aim:
• Measurement of soft double diffractive cross-section with particle ηmin visible to TOTEM T2 ( 4.7 < |ηmin | < 6.5 ≡ 3.4 < Mdiff < 8 GeV)
• ND background estimated scaling the MC prediction using a control sample from data dominated by ND (2T1+2T2 events)
• SD background estimated completely from data using a SD-dominated control sample (0T1+1T2) with protons in the RP
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 28
Soft Double Diffractive cross-section at 7 TeV Results from 7 TeV data:
• Preliminary
• the σDD uncertainty is dominated by events with |ηmin | outside detector acceptance
MC comparisons:
• Improvement expected with the 8 TeV data, including also the CMS information
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 29
b 25120 )5.67.4( min
h
DD
Central Diffraction (or DPE) TOTEM alone Correlation between leading protons and forward detector T2:
RP RPT2 T2
IPsector 45 sector 56
low ξ high ξ
1=Dp1/p1
2=Dp2/p2
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 30
Central Diffraction TOTEM alone
σCD estimation:
mb 1
)(
21
2
0 0
21
2,1
21
2
21
D
dtdt
ddtdt
eeCdtdt
d
CDCD
BtBtCD
Available data s=7 TeV and β* = 90m optics:
• trigger selection: 2 × RP
• nearly complete ξ-acceptance
• background: elastic, beam-halo + inelastic
• elastic: anti-elastic cuts, or use forbidden topologies (top-top, bottom-bottom)
• beam-halo: |y| > 11 ×σbeam → halo is negligible
B=7.8 1.4 GeV-2
Single arm CD event rate in RP integrated , acceptance corrected
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 31
TOTEM Preliminary
Central Diffraction TOTEM+CMS
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 32
Unprecedented properties:
• Mass of diffractive system X is double determined – By TOTEM Roman Pots MX = s ξ1 ξ2
– By CMS
• Double arm proton detection
Central Diffraction TOTEM+CMS TOTEM + CMS = unprecedented rapidity coverage: • CMS tracker : |η| < 2.5 • CMS calorimeters : |η| < 5.5 • TOTEM T1 : 3.1 < |η| < 4.7 • TOTEM T2 : 5.3 < |η| < 6.5 • CMS FSC : 6 < |η| < 8 Available data s = 8 TeV, β* = 90 m • CMS and TOTEM is consistent within resolution • MCMS(particle flow) = MTOTEM
• pCMS(particle flow) = pTOTEM
Low cross-section processes: • Background critical (pile-up) • More data needed
Pile-up removal • 0 or 1 vertex in CMS • RP near edge area removed (1 elastic proton + beam halo or SD) • ξ > 1.5 % • RP ξ predicts event topology in central detectors • FSC empty: QCD background protection • MX,CMS < MX,RP
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 33
Central Diffraction TOTEM+CMS Run / Event : 198903 / 3478279
• β* = 90 m
• Jets ET = 65, 45, 27 GeV
• ∑pT(CMS) = 3.4 GeV
• FSC empty both sides
• ξ - = -0.1, ξ + = -0.01
• M(pp) = 244 GeV
• MCMS = 219 GeV
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 34
Summary Total cross-section
Elastic Scattering
jet
jet
Diffraction: soft (and hard with CMS)
b
Forward physics
Measured at 7 and 8 TeV
Preliminary results • DD, CD, SD • Many analysis in progress !
Forward multiplicity distribution 7 and 8 TeV
Measured at 7 and 8 TeV 6 10-4 < |t| < 2.5 GeV2
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 35
TOTEM Consolidation & Upgrade program
Present : LHC in LS1
• Restart : 2015 at s=7 TeV → even higher luminosities → higher pile-up
• TOTEM interest to lower cross-section processes → higher lumi. → pile-up
How to deal with pile-up ?
• two units will be replaced hosting rotated (or pixel) detectors → multiple tracks can be resolved
• association of TOTEM and CMS tracks : two new units hosting timing detectors
RP147:
• relocated to 203-213 m → longer arm → better angular resolution
• 1 unit rotated by 8 degrees
Other upgrade activities:
• RP impedance optimization → reduce heating → reduce feedback on beam
• Secondary particle / shower production studies
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 36
Thank you for your attention !
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 37
Backup slides
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 38
ty-acceptance corrections
Missing acceptance in θy*
due to beam divergence Correction error (ty): 0.31 GeV2 : 30% 0.33 GeV2 : 11% 0.35 GeV2 : 2% 0.4 GeV2 : 0.8% 0.5 GeV2 : 0.1%
|t|<0.36 GeV2 excluded from analysis
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 39
ϕ-acceptance corrections
Critical at low t-acceptance limit
Total -acceptance correction
Accepted (t)
1 2 3 4 5 6
Accepted (t)
Diagonal 1
Diagonal 2
Θ*
|t|<0.36GeV2 excluded from analysis
No. t [GeV2] Θ* [rad] Accepted
(2 diag.) [°]
accept. correct. factor
1 0.33 1.65E-04 38.6 9.3±4.7%
2 0.36 1.71E-04 76.4 4.7±1.8%
3 0.60 2.21E-04 162.5 2.2±0.3%
4 1.00 2.86E-04 209.8 1.7±0.1%
5 1.80 3.83E-04 246.3 1.5
6 3.00 4.95E-04 269.0 1.3
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 40
Differential DPE distributions (uncorrected) RP reconstruction alone
[GeV] M 21 s
Unc
orre
cted
dN
/dM
1,2>3%
-t [GeV2]
Un
corr
ect
ed
dN
/dt 1
,2
Unc
orre
cted
dN
/d
1,2
1,2
1,2>3% all 1,2
proton 45 proton 56
proton 45 proton 56
-distribution t-distribution
M-distribution
acceptance loss acceptance difference
Hadron Structure'13 6/18/2013 Frigyes Nemes, TOTEM 41
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