inelastic cross section and forward particles multiplicity in totem

Inelastic Cross Section and Forward Particles Multiplicity in TOTEM

Giuseppe Latino (University of Siena & Pisa INFN)

(on behalf of the TOTEM Collaboration)

MPI 2012 CERN – December 3, 2012

1/20

TOTEM Physics Program OverviewTOTEM Physics Program OverviewStand-Alone

- TOTpp with a precision ~ 1-2%, simultaneously measuring (L ind. meth.):

Nel down to -t ~10-3 GeV2 and

Ninel with losses < 3%

- Elastic pp scattering in the range 10-3 < |t| ~ (p)2 < 10 GeV2

- Soft diffraction (SD and DPE)

- Particle flow in the forward region (cosmic ray MC validation/tuning)

CMS-TOTEM (largest acceptance detector ever built at a hadron collider) (CMS/TOTEM Physics TDR, CERN/LHCC 2006-039/G-124)

- Soft and hard diffraction in SD and DPE (production of jets, bosons, h.f.)

- Central exclusive particle production

- Low-x physics

- Particle and energy flow in the forward regionMPI 2012 – Dec. 3, 2012 G. Latino – TOTEM Inel. Xsec. and fwd Part. Multip 2/20

TOTEM Detector Setup @ IP5 of LHC (TOTEM Detector Setup @ IP5 of LHC (Same of CMSSame of CMS) )

CMSCMS

HF

T1:3.1 << 4.7

T2: 5.3 < < 6.5

Inelastic Telescopes:Inelastic Telescopes:reconstruction of tracks and interaction vertex;trigger capability with acceptance > 95 %

T1: 18 - 90 mrad

T2: 3 - 10 mrad

= - log(tg(/2))

~14 m10.5 m T1T1

T2T2

Detectors on both sides of IP5Detectors on both sides of IP5

RP220(RP147)ZDC

Elastic Detectors (Roman PotsElastic Detectors (Roman Pots):): reconstruction of elastically scattered and diff. pActive area up 1-1.5 mm from beam: 5-10 rad

HF

3/20MPI 2012 – Dec. 3, 2012 G. Latino – TOTEM Inel. Xsec. and fwd Part. Multip

p. 4

T1 (CSCs)

hit 1 mm

Vertical Pot

Vertical Pot

Vertical Pot

Vertical Pot

Horizontal Pots

RP 147Package of 10 “edgeless” Si-detectors hit 10 µm

T2 (GEMs)

hit 100 µm

TOTEM Detectors


Inelastic Cross Section @ 7 TeVInelastic Cross Section @ 7 TeV

T2

η

tracks

T2

η

η

Inelastic events in T2: classification - Tracks in both hemispheres: mainly non-Diffractive minimum bias (ND) and Double Diffraction (DD)

- Tracks in a single hemisphere: mainly single diffraction (SD) with MX > 3.4 GeV/c2

Optimized study of trigger efficiency and beam gas background corrections


Data sample - Oct. 2011 run with β* = 90 m: same data subsets used for the L-independent total cross section measurement

- T2 triggered events

- Low pile-up: (μ = 0.03)

Inelastic Cross Section @ 7 TeV: CorrectionsInelastic Cross Section @ 7 TeV: Corrections

σinelastic = 73.7 ± 0.1stat ± 1.7syst ± 3.0lumi mb


CERN-PH-EP-2012-352

Low-Mass Diffraction: T1+T2 AcceptanceLow-Mass Diffraction: T1+T2 Acceptance

T1+T2 (3.1 < || < 6.5) give an unique forward charged particle coverage @ LHC lower Mdiff reachable:minimal model dependenceon required corrections forlow mass diffraction

MPI 2012 – Dec. 3, 2012 G. Latino – TOTEM Inel. Xsec. and fwd Part. Multip

QGSJET-II-03:dN/dMdiff

MX > 3.4 GeV/c2 (T2 acceptance)

Several models studied: correction for low mass single diffractive cross-section based on QGSJET-II-03 (well describing low mass diffraction at lower energies), imposing observed 2hemisphere/1hemisphere event ratio and the effect of “secondaries”

Mx < 3.4 GeV = 3.1 ± 1.5 mb 7/20

Constraint on low mass diffraction cross-section:

Use total cross-section determined from elastic observables (via the Optical Theorem) no assumption on low mass diffraction

inel = tot – el = 73.2 1.3 mb

and the measured “visible” inelastic cross-section for || < 6.5 (T1, T2)

inel, || < 6.5 = 70.5 2.9 mb

to obtain the low-mass diffractive cross-section (|| > 6.5 or MX < 3.4 GeV)

inel, || > 6.5 = inel - inel, | < 6.5 = 2.6 2.2 mb

(or < 6.3 mb @ 95% CL) [MC: 3.1 1.5 mb]


Low-Mass Diffraction: Constraint from NLow-Mass Diffraction: Constraint from Nelel

(I) CMS L + Elastic Scattering + Optical Theorem depends on CMS luminosity , elastic efficiencies & ρ: no depenence on low mass diffraction

(small L bunches, * = 90 m, |t|min 210-2 GeV2): σinel = 73.5 1.6 mb

(large L bunches, * = 90 m, |t|min 510-3 GeV2): σinel = 73.2 1.3 mb

(II) (L -independent): Elastic Scattering + Inelastic Scattering + Optical Theorem eliminates dependence on luminosity, depends on & low mass diffraction models

using L- and -independent ratio: σel / σinel = Nel / Ninel = 0.354 0.009

=

0.1410.007

(Compete)


Inelastic Cross Section @ 7 TeV: Other Inelastic Cross Section @ 7 TeV: Other Meas.Meas.

σinel = 72.9 1.5 mb CERN-PH-EP-2012-353

CERN-PH-EP-2012-239

EPL 96 (2011) 21002

inel = tot – el

(see J. Kašpar talk for σel and σtot measurements)

Inelastic Cross Section @ 7 TeV: SummaryInelastic Cross Section @ 7 TeV: Summary


Excellent agreement among measurements:

- with different methods (understanding of systematic uncertainties and corrections)

- with other LHC experiments

(CERN-PH-EP-2012-353)

Same analysis strategy as for the measurement @ 7 TeV with the L –independent “method II”:

- tot = 101.7 2.9 mb

- Nel / Ninel = 0.362 0.011

Inelastic Cross Section @ 8 TeV: ResultsInelastic Cross Section @ 8 TeV: Results

Paper draft approved for submission to journal


July 2012: runs at * = 90 m

inel = 74.7 1.7 mb

T2 alignment-- Internal alignment two different track-based methods (HIP and Millepede) implemented in order to resolve misalignment (x-, y-shifts) among detectors in a quarter

- - QQuarter-quarter alignment using tracks in the overlap region

- - GGlobal alignment each arm aligned (tilts and shifts) respect to the nominal position by imposing the symmetry of the “beam pipe shadow” on each detector plane

Charged Particle Pseudo-Rapidity Density Charged Particle Pseudo-Rapidity Density ((dNdNchch/d) @ 7 TeV /d) @ 7 TeV

z IP

x

Final precision achieved: ~ 1 mm (x,y-shifts); ~ 0.4 mrad (plane tilts) 12/20MPI 2012 – Dec. 3, 2012 G. Latino – TOTEM Inel. Xsec. and fwd Part. Multip

May 2011 run, * = 3.5 m, low pile-up ( 0.03)

dNdNchch/d in T2: Analysis Highlights/d in T2: Analysis HighlightsData sample: events at low luminosity and low pile-up, triggered with T2 (5.3 < || < 6.5)

Selection: at least one track reconstructed in T2

Primary particle definition: charged particle with > 0.310-10 s, pT > 40 MeV/c

Primary particle selection: -primary/secondary discrimination, data-driven based on reconstructed track parameters (ZImpact)

Primary track reconstruction efficiency: - evaluated as a function of the track and pad multiplicity, MC-based - efficiency of 80% - fraction of primary tracks within the cuts of 75% – 90% ( dependent)

Un-folding of () resolution effects: MC driven bin “migration” corrections

Systematic uncertainties (< 10%): dominated by primary track efficiency and global alignment correction uncertainty


Track reconstruction in T2 is challenging because of the large amount of charged particles generated by the interaction with the material placed between the IP and T2

A detailed revision of the volumes and of the GEANT setting was necessary

Material contributing to secondaryparticle generation: Left: BP flange and ion-pumps. Right: BP cone at =5.53 and the lower edge of HF

Effect of the BP on the hit didtribution

IP

H FH F

T2 telescope

90% (80% ) of the signal

(tracks) in T2 is given by secondaries

Secondary Particles in T2Secondary Particles in T2

MPI 2012 – Dec. 3, 2012 G. Latino – TOTEM Inel. Xsec. and fwd Part. Multip 14/20

- A fit on the distribution of the track Zimpact parameter is used to separate primary from secondary tracks

- We know from MC and data comparison the shape of the primary and secondary track Zimpact distribution (double-gaussian for primaries, exponential for secondaries)

- A large part of the secondary contribution can be therefore extracted from the primary region by fitting the track-ZImpact distribution. The fit is repeated for each bin.

Track Z-Impact definition

90°

T2-track

dNdNchch/d in T2: Primary Track Selection/d in T2: Primary Track Selection

One quarter distribution

Exponential secondary

Double GaussianPrimary

Z-Impact distribution (one quarter, one bin)

Z0·sign()

< 13.5 m


Multiple scattering and magnetic field effects turn out to determine the primary charged particle PT acceptance of T2

At PT = 40 MeV/c the efficiency, including the Zimpact cut, is 80%. This is also the value which minimizes the inclusion of tracks with PT < 40 MeV/c and the losses on higher PT tracks

Particle PT (GeV/c)

Tracking Performance: PTracking Performance: PTT AcceptanceAcceptance


Published: EPL 98 (2012) 31002

TOTEM measurements “combined” with the other LHC experiments

TOTEM measurements compared to MC predictions

dNdNchch/d in T2: Results/d in T2: Results

None theoretical model fully describes the data. Cosmic Ray (CR) MCs show a better agreement for the slope: - SYBILL (CR): 4–16% lower - QGSJET-II (CR): 18-30% higher

High “visible” fraction of inelastic cross section:

95% inel

- Diffractive events with MDiff

> 3.4 GeV

- ND events > 99%


• combined dNch/d and multiplicity correlations• hard diffraction: p + di-jets (* = 90m)

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, nel with CMS,soft & semi-hard diffraction,correlations

Date Trigger Inelasticevents

May 1 T2 || BX ~5 M no RP

dNch/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

Joint Data Taking with CMSJoint Data Taking with CMS

Analyses ongoing:

2011 Ion run: proof of principle

2012: Ist realization of common running

• CMS TOTEM trigger exchange

• Offline data “synchronization” (orbit and bunch #) + “merging” (n-tuple level)


T2[T1]

Ongoing Activity on dNOngoing Activity on dNchch/d Measurement/d Measurement

Analyses in progress:• T1 measurement @ 7 TeV (3.1 < || < 4.7)

• Combined analysis CMS + TOTEM (0 < || < 6.5) on low-pileup run of May 2012 (@ 8 TeV): common trigger (T2, bunch crossings), both experiments read out

• NEW: parasitical collision at β* = 90 m (July 2012, 8 TeV) vertex @ ~11m shifted acceptance for T2: - extend range up to 7.3 (under study) - cross-check with T1 results in the 3.8-4.8 range (ongoing)


16

TOTEM detectors fully commissioned and operative 2011 data taking (s = 7 TeV) in special runs with different beam

conditions (* = 3.5, 90 m) allowed the measurements of:- inelastic p-p cross-section (with different methods)- dNch/d with T2 (5.3 < || < 6.5)

- analysis ongoing for the dNch/d measurement with T1 (3.1<||<4.7)

2012 data taking (s = 8 TeV) in special runs: - measurement of inel with L-independent method - first joint TOTEM/CMS data taking with common triggers and both experiments read out: analysis ongoing on dNch/d measurement on the full range (|| < 6.5) - special run with displaced vertex @ 11m: potentiality of dNch/d measurement with T2 in the range 3.8 < || < 4.8 (and maybe up to 7.3)

Possibility of dNch/d measurement for different inelastic topologies (ND, SD, DD) under study

Looking forward for more data a higher s

Summary & Summary & OutlookOutlook


Backup Slides

Services routing:From Castor to Racks

Patch Panels

T2

Services routing:From Castor to Racks

Patch Panels

T2

T1

T2 Castor (CMS)

Services routing:

From Castor to Racks

Patch Panels

T2

Services routing:

From Castor to Racks

Patch Panels

T2

T2

Castor (CMS)

CMST1

Leading Protons measured at +147m & +220m from IP

Leading Protons measured at-147m & -220m from IP

TOTEM Experiment

TOTEM & CMS @ IP5 of LHC

TOTEM Collaboration: Bari, Budapest, Case Western Reserve, CERN, Genova, Helsinki, Penn U., Pisa/Siena, Prague, Tallin (~ 80 physicists)

B1

Each arm: 5 planes with 3 coordinates/plane, each formed by 6 trapezoidal CSC detectors 3 degrees rotation and overlap between

adjacent planes Trigger with anode wires Digital readout (VFAT) for ~ 13.5K ch. Hit Resolution: ~ 1 mm

T1 TelescopeT1 Telescope

1/4 of T1

Ageing studies at CERN GIF: no loss of performance during 12-month test, with ~ 0.07 C/cm accumulated charge on wires, a dose equivalent to ~ 5 years at Linst=1030 cm-2s-1

Fully commissioned and operative

B2

Each arm: 10 planes formed by 20 triple-GEM

semi-circular modules, with “back-to-back assembly and overlap between modules

Test Beam

T2 TelescopeT2 Telescope

Castor Calorimeter (CMS)

~ 0.4 m

T2: “GEM” Technology

Double readout layer: Strips for radial position (R); Pads for R,

Trigger from Pads (1560/chamber)

Digital readout (VFAT) for ~ 41.4K ch.

Hit Resolution: R ~ 100 m, ~ 1o

pads

strips

GEM Technology: Gas Detector Rad-hard High rate Good spatial and timing resolution

T2 Triple GEM technology adequate to work at least 1 yr at L=1033 cm-2s-1


B3

Horizontal Pot: extend acceptance; overlap for relative alignment using common track

Absolute (w.r.t. beam) alignment from beam position monitor (BPM)

Beampipes

Roman Pots (I)Roman Pots (I)

Each RP station has 2 units, 5m apart.Each unit has 3 insertions (‘pots’): 2 vertical and 1 horizontal

Units installed into the beam vacuum chamber allowing to put proton detectors as close as possible to the beam

Protons at few rad angles detected down to 5 + d from beam (beam ~ 80m at RP)

‘Edgeless’ detectors to minimize d

Horizontal Pot Vertical Pot BPM

B4

200m thick200m thick

beam

Roman Pots (II) Roman Pots (II) Each Pot:

10 planes of Si detectors 512 strips at 45o orthogonal Pitch: 66 m Total ~ 5.1K channels Digital readout (VFAT): trigger/tracking Hit Resolution: ~ 10 m

Readout chip VFAT

Edgeless Si detector:

50 μm of dead area

Integration of traditional Voltage Terminating Structure with the Current Terminating Structure

Detectors expected to work

up to Lint ~ 1 fb-1


B5

CMS/TOTEM Common Physics Program

CMS + TOTEM largest acceptance detector ever built at a hadron collider: the large coverage and p detection on both sides allow the study of a wide range of physics processes in diffractive interactions

Charged particles

Energy flux

TOTEM+CMS

dE/d

dE/d

d

Nch/d

Ro

ma

n P

ots

T1,T2 T1,T2 Ro

ma

n P

ots

LHC, inelastic collisions

CMS

CMS

M

MDouble Pomeron Exchange

Double Diffraction

Single Diffraction

Elastic Scattering

~ 60 mb

18 - 35 mb

10 - 16 mb

4 - 14 mb

0.2 - 1.5 mb

<< 1 mb

B6

MX > 3.4 GeV/c2 (T2 acceptance)

S

D d

SD/d

SIBYLL/PYTHIA8

QGSJET-II-4

low mass contribution

S. OstapchenkoarXiv:1103.5684v2 [hep-ph]

Low-Mass Diffraction: MC Predictions

Several models studied: correction for low mass single diffractive cross-section based on QGSJET-II-03 (well describing low mass diffraction at lower energies), imposing observed 2hemisphere/1hemisphere event ratio and the effect of “secondaries”

Mx < 3.4 GeV = 3.1 ± 1.5 mb B7

A = 506 23.0syst 0.9stat mb/GeV2

A = 504 26.7syst 1.5stat mb/GeV2

B = 19.9 0.27syst 0.03stat GeV-2

||el / tBeAdtd

|t|dip= 0.53 GeV2

~ |t|7.8

25.4 ± 1.0lumi ± 0.3syst ± 0.03stat mb (91% directly measured)24.8 ± 1.0lumi ± 0.7syst ± 0.2stat mb (67% directly measured)

Integrated elastic cross-section:

El = El, Meas. + El, Extr.

(L from CMS)

Elastic Scattering Differential Cross-Section @ 7 TeVElastic Scattering Differential Cross-Section @ 7 TeV

EPL 95 (2011) 41001

EPL 96 (2011) 21002

CERN-PH-EP-2012-239 Analysis ongoing on additional data set (2 GeV2 < |t| < 3.5 GeV2)

None of the theoretical models really fit the data

B8

Inelastic Cross Section @ 7 TeV: SummaryInelastic Cross Section @ 7 TeV: Summary

B9

CERN-PH-EP-2012-352CERN-PH-EP-2012-353CERN-PH-EP-2012-239EPL 96 (2011) 21002

•A good description of the forward particle multiplicity and density produced in p-Air collision is important for the analysis of the Extensive Air Shower produced when a High Energy CR interacts in the athmosphere.

•The energy and mass of the primary CR can be understood from measurement on Earth thanks to MCs which simulate the air shower.

•7 TeV pp collisions at LHC correspond to pCR-pAIR collisions with pCR of ~25 PeV.

The CR connection: tuning of the MC generator used in the Extensive Air Showers simulations

Forward Physics: Forward Physics: importance of the dN/dimportance of the dN/d measurement measurement

B10

The Beam Pipe “Shadow” on T2

IP5HF

HF

HF

HF Beam Pipe cone at ~ 5.54

(>100 radiation lengths)

B11

|ZImpact| < 5m

Definition of thetrack ZImpact parameter:

T2 inelastic event detection efficiency (at least a ch. particle generated in the T2 acceptance): 99.5%

Average data APM (7 TeV)

Bin width: 0.05

APM:Average Pad-ClusterMultiplicity

T2 Tracking performance: T2 Tracking performance: efficiencyefficiency Event reconstruction

efficiency

B12

Track ZImpact before and after the global misalignment correction in data and in a MC, where the misalignment geometry is simulated:

Maximum tilt angle measured in the data = 8mrad (T2 acceptance: 3-10 mrad !)

Tuned MC Data

primaries

secondaries

Primary/secondary separation is impossible without the global alignment.

Importance of Global Misalignment

B13

Resolution: RMS of the difference between the reconstructed and the generated Vtx smearing Z= 5 cm, 2<E<80 GeV -

Two estimators of were studied: IMPIMP and and RZRZ

IMP = average of the of the track hits (each one calculated with the vertex at

(0,0,0))

= pseudorapidity of the track calculated with the polar angle of the track in the

RZ plane

RZ

IMP

Only tracks with|ZImpact|< 5m are included

IMP implicitly performs a vertex constraint. Smaller at high because of the smaller contribution of B and Vtx smearing. RZ grows as η ∼ θ/θ, more dependent on misalignment.

B14

IMP

RZ

Tracking Performance: ResolutionTracking Performance: Resolution

1. Data/MC comparison of “half quarter” trk efficiencies2. Effect of wrong misalignment parameters on the measured dN/d3. Maximum variation of the secondaries contamination from different MC.

Evaluation method

4. Fit/fitting-interval uncertainty

5. MC spectrum and B intensity variation

6. Different MC estimates7. Data/MC discrepancy on the effect of the cut on the track 2-probability.8-9. Dedicated analysis on bunch-crossing samples

(*) not all the contributions have been added in quadrature

(*)

Com

mon

to a

ll

the

quar

ters

Qua

rter

depe

nden

tdNdNchch/d in T2: Systematic Errors/d in T2: Systematic Errors

B15

RP insertions in normal physics runs (* = 0.6 m) - hard diffraction together with CMS (high diffractive masses reachable) - proton acceptance: > 2-3 %, any t - study of closest possible approach of the hor. 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 not aligned) study soft central diffraction final states with 2 leading protons defining Pomeron-Pomeron mass M2 = x1 x2 s (good x resolution at * = 0.6 m s(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)

Runs Planned for 2012-13

B16

[K. Oesterberg, pA @ LHC workshop, June 2012]

pA Minimum Bias PhysicspA Minimum Bias Physics

B17

inelastic cross section and forward particles multiplicity in totem

Documents