Transcript Status of the TOTEM Experiment and Latest Results Hubert Niewiadomski on behalf of the TOTEM Collaboration LHCC, 15 June 2011

Status of the TOTEM Experiment
and Latest Results
Hubert Niewiadomski
on behalf of the TOTEM Collaboration
LHCC, 15 June 2011
Experimental Setup @ IP5
Inelastic telescopes: charged particle
& vertex reconstruction in inelastic events
T1: 3.1 <  < 4.7
T2: 5.3 <  < 6.5
IP5
HF
(CMS)
~ 10 m
~ 14 m
T1
CASTOR (CMS)
T2
Roman Pots: measure elastic & diffractive protons close to outgoing beam
IP5
RP147
RP220
T1
T2
RP 147
The TOTEM experiment is completely
installed and running
•
•
•
•
•
•
All Roman Pots at 147 and 220m installed (24 pots)
T1 detectors are installed on both sides
T2 detectors are installed on both sides
Trigger system based on all detectors is running
DAQ is running with an event rate capability of 1 kHz
Special runs with dedicated b* and bunch structures
are prepared
Beam based alignment of RPs @220m and data taking (T1,T2,RP220m)
(18 May 2011)
Beam Loss Data
Beam intensity
Scraping exercise:
RP220 approached the low intensity beam in 10 mm steps
RP220 now ready for routine insertions in 2011
RP approach
x, y
Vert Pot Position (mm)
Data taking with RPs @ 220 close to
the beams
- vertical RPs @ 5σ = 2.2 mm
- horizontal RPs @ 7σ = 1 mm
- low pile-up
Alignment of RP147 planned in August
T2 data
2011
Raw data
Very good agreement:
- left and right side
- bunch and active trigger
Pythia
PhoJet
Unfolded
Green band after vertex cuts
‘Plus’ and ‘minus’ T2 sides superimposed
- Bunch crossing trigger
- T2 detector trigger
Taken during scraping exercise
only low intensity bunches of 1010 p (low pile-up)
Low luminosity runs 2010
Preliminary dN/d results (T1)
• 3 short periods of data taking with useful conditions for T1 (L = 1028 – 1030 cm–2 s–1):
March (2.76 TeV), May (7 TeV)
• 25 million events collected with different configurations
• Data analysis in progress
• T1 ready for physics
 Distributions (uncorrected)
Vertex reconstruction
7 TeV
Vertex reconstruction is effected
by the CMS magnetic field
Symmetric distributions obtained
– a good starting point
ELASTIC pp SCATTERING
t-range: 0.36 – 3 GeV2
Elastic pp scattering
• Several runs were taken during 2010
with different distances of the Roman pots to the beam center
• The 7 s runs were analyzed
• The 18 s runs with a total luminosity of 5.8 pb-1 will follow
Luminosity
25 s
Integrated
luminosity
1.5 nb-1
20 s
185 nb-1
18 s
5800 nb-1
RP dist.
Analysed data files
7s
p. 9
Karsten Eggert–
9.5 nb-1
important for
large t
Proton reconstruction
• Both angle projections reconstructed: Θx* and Θy*
– Θx* from Θx @ RP220 (through dLx/ds)
– Θy* from y @ RP220 (through Ly)
Θx = dLx/ds Θx*
y = Ly Θy*
→ Excellent optics understanding
– Magnet currents measured
– Measurements of optics parameters with elastic scatt.
•
•
•
Θleft* = Θright* (proton pair collinearity)
Proton position ↔ angle correlations
Lx=0 determination, coupling corrections
→ Fine alignment
– Alignment between pots with overlapping tracks (1μm)
– Alignment with respect to the beam – scraping exercise
(20μm)
– Mechanical constraints between top and bottom pots
(10μm)
Track based alignment
Cuts and data reduction
• Topology
Intergrated luminosity : 6.2 nbarn-1
– near and far units
– diagonals
• Low || selection (3σ)
–
–
–
–
|xRP,45|<3σx @ Lx,45=0
|xRP,56|<3σx @ Lx,56=0
corr. yRP216,45  yRP220,45
corr. yRP216,56  yRP220,56
• Elastic collinearity (3σ)
– θx,45*  θx,56*
– θy,45*  θy,56*
Total triggers
5.28M
Reconstructed tracks &
elastic topology
293k
Low || selection
70.2k
Collinearity cuts
66.0k
showers
Diagonals analysed independently
Proton tracks of a single diagonal
(left-right coincidences)
Sector 56
t = -p2 q2
 = Dp/p
Sector 45
y = Ly Qy
x = Lx Qx +  D
Lx ~ 0
Cuts and data reduction
• Topology
Intergrated luminosity : 6.2 nbarn-1
– near and far units
– diagonals
• Low || selection (3σ)
–
–
–
–
|xRP,45|<3σx @ Lx,45=0
|xRP,56|<3σx @ Lx,56=0
corr. yRP216,45  yRP220,45
corr. yRP216,56  yRP220,56
• Elastic collinearity (3σ)
– θx,45*  θx,56*
– θy,45*  θy,56*
Total triggers
5.28M
Reconstructed tracks &
elastic topology
293k
Low || selection
70.2k
Collinearity cuts
66.0k
showers
Low  = Dp/p cuts
|x| < 3σx @ Lx = 0
yRP near,45  yRP far,45
(dLy/ds0)
Cuts and data reduction
• Topology
Intergrated luminosity : 6.2 nbarn-1
– near and far units
– diagonals
• Low || selection (3σ)
–
–
–
–
|xRP,45|<3σx @ Lx,45=0
|xRP,56|<3σx @ Lx,56=0
corr. yRP216,45  yRP220,45
corr. yRP216,56  yRP220,56
• Elastic collinearity (3σ)
– θx,45*  θx,56*
– θy,45*  θy,56*
Total triggers
5.28M
Reconstructed tracks &
elastic topology
293k
Low || selection
70.2k
Collinearity cuts
66.0k
showers
Elastic collinearity cuts
Data outside the 3σ cuts used for background estimation
Background and resolution determination
–– signal
–– background
–– combined
B/S = (8±1)%
σ*=17.8mrad
(beam divergence)
Data
Combined
background (t)
-t [GeV2]
Dθx/sqrt(2)
Signal to background normalisation
(also as a function of Dθy)
σ* → t-reconstruction resolution:
s (t )
t
0.4 GeV 2 : 14%
2 ps *
=
: 1 GeV 2 : 8.8%
t
3 GeV 2 : 5.1%
Signal vs. background (t)
|t|=0.4GeV2: B/S = (11±2)%
|t|=0.5GeV2: B/S = (19±3)%
|t|=1.5GeV2: B/S = (0.8±0.3)%
ty-acceptance corrections
|t|<0.36GeV2 removed
Missing acceptance in θy*
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%
-acceptance correction
Total -acceptance correction
Accepted (t)
t [GeV2]
Θ* [rad]
1
2
3
4
5
6
0.33
0.36
0.60
1.00
1.80
3.00
1.65E-04
1.71E-04
2.21E-04
2.86E-04
3.83E-04
4.95E-04
38.6
76.4
162.5
209.8
246.3
269.0
Diagonal 1
12 3 4

No.
Accepted 
(2 diag.) [°]
5
6
Θ*
|t|<0.36GeV2 removed
Accepted (t)
Diagonal 2
Critical at low t-acceptance limit
 accept.
correct.
factor
9.3±4.7%
4.7±1.8%
2.2±0.3%
1.7±0.1%
1.5
1.3
Final unfolded distribution
| Systematic normalisation
uncertainty30%
Elastic Scattering – from ISR to Tevatron
ISR
~ 1.7 GeV2
~ 0.7 GeV2
~1.5 GeV2
Comparison to some models
B
(t=-0.4 GeV2)
tDIP
t-n
[1.5–2.5 GeV2]
20.2
23.3
0.60
0.51
5.0
7.0
22.0
0.54
8.4
25.3
20.1
0.48
0.72
0.53 ±
0.01
10.4
4.2
23.6 ± 0.5
Better statistics at large t needed
7.8 ± 0.3
Future analyses of existing data
1. RP
– 18 s 2010 data (5.8 pbarn-1)
– Double Pomeron Exchange, RP +T1 and T2 (2011 data from 6 low L pilots)
2. Inelastic detectors T1 and T2 (data from 2011)
– Pseudorapidity distributions (including RP information)
– Multiplicity distributions and correlations
Future runs 2011
1. RP 220 m fully validated (14 s vert., 17 s horiz. in normal runs):
(large-t elastic scattering, β*=1.5 m)
2. RP 147 m beam based alignment with data taking (August)
(diffraction)
3. β* = 90 m optics
– First MD (done): successful for separated beams
– Next MD (28. June): establish collisions and ~1hour data taking for optics
diagnostics
– Physics starting in August / September
•
•
Low-t (10 -2 GeV2) elastic scattering
Total cross-section (extrapolation to t=0 possible)
BACKUP
Outlook: Measurement of r in the Coulomb-nuclear
Interference Region?
Aim: get also the last ingredient to stot from measurement rather than theory
(eN = 3.75 mm rad)
(eN = 1 mm rad)
might be possible at sqrt(s)=7 TeV with RPs at 6 s
incentive to develop very-high-b* optics before reaching 14 TeV !
e.g. try to use the same optics principle as for 90m and unsqueeze further.
OPTICS
Optics verification
Triplet
dLx/ds
dLy/ds
MQY MQML
dLy/ds|s=220m measured
by TOTEM
Lx
Ly
s

dLy ( )
L
(
s
)
=
 L y ( 0) = 0
 y
0 d d  C1


, with  dLy
 dL ( s ) s
 y
 ds (0) = 1
=  Ly ( )k ( )d  C2
 ds
0
s: Lx=0 measured
by TOTEM
s: Lx(s)==0 determination
• Four fits per diagonal, 8 in total, diagonals averaged
Top 45 bottom 56, 45 near
s=214.463 m
Top 45 bottom 56, 45 far
s=220 m
a=2.229
a=-3.142
Interpolation: Lx(s) = 0 for s = 217.8 m (nominally 222.1m)
Θy vs. y, coupling , beam 1
Preliminary fits, fit direction rather needs to be orthogonal,
better numbers from Jan’s alignment needed
(dLy/ds) / Ly near =3.9210-3 m-1 5 %
Nominally: 2.710-3 m-1
Constraint for triplet strenghts matching
re14/re34 far=36 mrad5 %
Nominally: 0
Constraint for triplet rotation matching
Beam 2
• (dLy/ds) / Ly=2.61510-3 m-1 5 % (nominally 1.30410-3 m-1)
• re14/re34 far=31.8 mrad 5 % (nominally 0)
Matched parameters
• Perturbation of (nominal) actual LHC settings
– 30 parameters per beam
– Magnet positions, rotations, k
– Beam energy, displacement, crossing angle, harmonics...
• Selected fitted parameters
–
–
–
–
6 strengths per beam (MQXA, MQXB, MQXB, MQXA, MQY, MQML)
6 corresponding rotations per beam
Mean  per beam
Total of 26 fitted parameters
Constraints
• TOTAL of 36
• LHC design constraints (a total of 26):
– sigma(k)/k = 0.1%
– sigma (rot) = 1mrad
– Sigma()/  = 10-3
• Measured constraints of individual arms (a total of 8):
– (dLy/ds)/Ly; near unit rotation (coupling); far unit rotation (coupling)
– s: Lx==0 (1 m precision)
• Measured elastic scattering kinematics constraints between
arms (a total of 2):
– Ratio of Ly56 / Ly45 (0.2 % precision)
– Ratio of (dLx/ds 56) / (dLx/ds 45) (0.5 % precision)
Matching solution
56
dLx/ds Ly [m]
RP215
RP220
D RP215
D RP220
-0.311962
-0.311962
-2.84%
-2.84%
22.1464676 0.0432331
22.6191755 0.0396463
+0.78%
+0.81%
45
dLx/ds Ly [m]
RP215
RP220
D RP215
D RP220
-0.314508
-0.314508
-4.51%
-4.51%
34
33
35 36 2
1
2
3
31
Principle Component Analysis (PCA) ideally should
be applied
ROT [mrad]
20.3883272 0.0400268
20.6709463 0.0372828
+10.19%
+10.79%
2/NDF = 25.8/(36-26)=2.6
(would be lower in correlations are elmininated)
Matching results within
the LHC tolerance
4
25
5
1.5
32
ROT [mrad] Strong correlations between fitted parameters
24
6
7
1
30
8
28
11
26
12
25
13
24
14
23
15
22
21 20
19
18 17
16
Abs(Pulls) of constraints
3
4
5
22
10
27
2
1
6
9
0
1
1.5
23
0.5
29
26 2
0.5
All constraints
21
7
Fitted parameters
0
20
8
19
9
18
10
17
11
16
15
14
13
12
Abs(Pulls) of fitted parameters
ANALYSIS STEPS DETAILED
Analytical unfolding
Smearing only due to beam divergence
Detector resolution negligible
(divergence uncertainty)
Verified by MC based approach
Verified by stringent selection cuts
Unfolding verification
MC vs. Analytical unfolding
Data transformations (after selection cuts)
diagonal top 45 bottom 56 alone
Raw data
Acceptance corrected
4
5
6
1
2
1 – raw data (signal + background)
2 – estimated background
3
3 – estimated background acceptance corrected
4 – raw data acceptance corrected
5 – raw data acceptance corrected - background
6 – final unfolded distribution
The Roman Pot System at 220 m and 147 m
fully installed
TOTAL: 24 pots
p. 38
Karsten Eggert–
Installation of the RP system at 147 m
p. 39
Karsten Eggert–