2012 LHC Days in Split, Croatia

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–