status of the totem experiment and latest results
DESCRIPTION
Status of the TOTEM Experiment and Latest Results. Hubert Niewiadomski on behalf of the TOTEM Collaboration. LHCC, 15 June 2011. Inelastic telescopes: charged particle & vertex reconstruction in inelastic events. T1: 3.1 < < 4.7 T2: 5.3 < < 6.5. HF (CMS). IP5. ~ 10 m. T1. - PowerPoint PPT PresentationTRANSCRIPT
Status of the TOTEM Experiment and Latest Results
Hubert Niewiadomskion behalf of the TOTEM Collaboration
LHCC, 15 June 2011
IP5
RP147 RP220
Roman Pots: measure elastic & diffractive protons close to outgoing beam
Inelastic telescopes: charged particle & vertex reconstruction in inelastic events
IP5
T1: 3.1 < < 4.7
T2: 5.3 < < 6.5
~ 10 m
~ 14 m T1 CASTOR (CMS)
HF (CMS)
T2
Experimental Setup @ IP5
T2
T1
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)
Data taking with RPs @ 220 close to the beams - vertical RPs @ 5σ = 2.2 mm - horizontal RPs @ 7σ = 1 mm - low pile-up
Scraping exercise: RP220 approached the low intensity beam in 10 mm stepsRP220 now ready for routine insertions in 2011
Beam Loss Data
Vert Pot Position (mm)
x, y
Beam
inte
nsity
Alignment of RP147 planned in August
RP approach
T2 data
Taken during scraping exercise only low intensity bunches of 1010 p (low pile-up)
Raw data
‘Plus’ and ‘minus’ T2 sides superimposed - Bunch crossing trigger - T2 detector trigger
Very good agreement: - left and right side - bunch and active trigger
Green band after vertex cuts
Pythia
PhoJet
Unfolded
Low luminosity runs 2010
2011
Preliminary dN/dh results (T1)
Vertex reconstructionh Distributions (uncorrected)
Vertex reconstruction is effected by the CMS magnetic field
Symmetric distributions obtained – a good starting point
• 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
7 TeV
ELASTIC pp SCATTERING t-range: 0.36 – 3 GeV2
Karsten Eggert–
Elastic pp scattering
p. 9
25 s 1.5 nb-1
20 s 185 nb-1
18 s 5800 nb-1
7 s 9.5 nb-1
Luminosity
• 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
Analysed data files
Integrated luminosity
RP dist.
important for large t
Proton reconstruction• Both angle projections reconstructed: Θx
* and Θy*
– Θx* from Θx @ RP220 (through dLx/ds) Θx = dLx/ds Θx
*
– Θy* from y @ RP220 (through Ly) 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
• Topology– 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
Intergrated luminosity : 6.2 nbarn-1
Cuts and data reduction
showers
Diagonals analysed independently
Sector 45
Sector 56 t = -p2 q2
= xDp/p
y = Ly Qy
x = Lx Qx + x D Lx ~ 0
Proton tracks of a single diagonal(left-right coincidences)
• Topology– 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
Intergrated luminosity : 6.2 nbarn-1
Cuts and data reduction
showers
|x| < 3σx @ Lx = 0 yRP near,45 yRP far,45
(dLy/ds0)
Low = Dp/p cuts
• Topology– 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
Intergrated luminosity : 6.2 nbarn-1
Cuts and data reduction
showers
Elastic collinearity cuts
Data outside the 3σ cuts used for background estimation
signal
background signal
background
Background and resolution determination
B/S = (8±1)%σ*=17.8rad(beam divergence)
|t|=0.4GeV2: B/S = (11±2)%|t|=0.5GeV2: B/S = (19±3)%|t|=1.5GeV2: B/S = (0.8±0.3)%
–– signal–– background–– combined
Signal to background normalisationθx/sqrt(2)
σ* → t-reconstruction resolution:
:2)( *
t
p
t
t
%1.5:GeV 3
%8.8:GeV 1
%14:GeV 4.0
2
2
2
Combined background (t)
-t [GeV2]
(also as a function of θy)
Data
Signal vs. background (t)
Missing acceptance in θy*
Beam diverge
nce
|ty | (diagonal 2)
|ty | (diagonal 1)
ty-acceptance corrections
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|<0.36GeV2 removed
-acceptance correction
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 removed
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 1.56 3.00 4.95E-04 269.0 1.3
Final unfolded distribution
| Systematic normalisation uncertainty30%
Elastic Scattering – from ISR to Tevatron
~1.5 GeV2
~ 0.7 GeV2
~ 1.7 GeV2
ISR
Comparison to some modelsB
(t=-0.4 GeV2) tDIPt-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
Future analyses of existing data1. 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
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)
Future runs 2011
BACKUP
Outlook: Measurement of r in the Coulomb-nuclear Interference Region?
Aim: get also the last ingredient to stot from measurement rather than theory
might be possible at sqrt(s)=7 TeV with RPs at 6 sincentive 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.
(eN = 3.75 mm rad)
(eN = 1 mm rad)
OPTICS
Optics verification
dLx/dsdLy/ds
LxLy
1)0(
0)0( with ,
)()()(
)()(
2
0
1
0
ds
dLL
CdkLds
sdL
Cdd
dLsL
y
y
s
yy
sy
y
Triplet
MQY MQML
dLy/ds|s=220m measuredby TOTEM
s: Lx=0 measuredby TOTEM
s: Lx(s)==0 determination• Four fits per diagonal, 8 in total, diagonals averaged
Top 45 bottom 56, 45 nears=214.463 m
Top 45 bottom 56, 45 fars=220 m
a=-3.142
a=2.229
Interpolation: Lx(s) = 0 for s = 217.8 m (nominally 222.1m)
Θy vs. y, coupling , beam 1
(dLy/ds) / Ly near =3.9210-3 m-1 5 %Nominally: 2.710-3 m-1
re14/re34 far=36 mrad5 %Nominally: 0
Constraint for triplet strenghts matching Constraint for triplet rotation matching
Preliminary fits, fit direction rather needs to be orthogonal, better numbers from Jan’s alignment needed
Beam 2• (dLy/ds) / Ly=2.61510-3 m-1 5 % (nominally 1.30410-3 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
1 2 34
56
7
8
9
10
11
12
1314
1516
171819202122
2324
25
26
27
28
29
30
3132
3334
35 36
0
1
2
All constraints
1 23
4
5
6
7
8
9
10
1112
13141516
17
18
19
20
21
22
23
2425
26
0
1
2
Fitted parameters
Strong correlations between fitted parameters
Principle Component Analysis (PCA) ideally should be applied
2/NDF = 25.8/(36-26)=2.6 (would be lower in correlations are elmininated)
Matching results within the LHC tolerance
56 dLx/ds Ly [m] ROT [mrad]RP215 -0.311962 22.1464676 0.0432331RP220 -0.311962 22.6191755 0.0396463D RP215 -2.84% +0.78%D RP220 -2.84% +0.81%
45 dLx/ds Ly [m] ROT [mrad]RP215 -0.314508 20.3883272 0.0400268RP220 -0.314508 20.6709463 0.0372828D RP215 -4.51% +10.19%D RP220 -4.51% +10.79%
Abs(Pulls) of constraints Abs(Pulls) of fitted parameters
ANALYSIS STEPS DETAILED
Analytical unfolding
(divergence uncertainty)
Verified by MC based approach Verified by stringent selection cuts
Smearing only due to beam divergenceDetector resolution negligible
Unfolding verificationMC vs. Analytical unfolding
Data transformations (after selection cuts)diagonal top 45 bottom 56 alone
2
1
3
456
1 – raw data (signal + background)2 – estimated background
Raw data Acceptance corrected
3 – estimated background acceptance corrected4 – raw data acceptance corrected5 – raw data acceptance corrected - background6 – final unfolded distribution
Karsten Eggert–
The Roman Pot System at 220 m and 147 m fully installed
p. 38
TOTAL: 24 pots
Karsten Eggert– p. 39
Installation of the RP system at 147 m