status of the totem experiment and latest results

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