p. 1Mario Deile –

DIS 2004DIS 2004

Mario Deile

CERN

on behalf of the TOTEM Collaboration

16.04.2004

TOTEM: Forward Physics at the LHC

p. 2Mario Deile –

• Elastic p-p scattering cross-section d/dt in the range 10-3 GeV2 < –t < 10 GeV2

• Total p-p cross section at 14 TeV with 1% uncertainty using the Optical Theorem (luminosity independent method)

• Diffractive events (together with CMS).• Absolute luminosity measurement and calibration of

CMS luminosity monitors

Physics Objectives of TOTEM

p. 3Mario Deile –

Detector Configuration

~14 m

CMSCMS T1:3.1 << 4.7

T2: 5.3 < < 6.5

10.5 m T1T1 T2T2

RP1RP1 RP2RP2 RP3RP3

220 m220 m180 m180 m147 m147 m

p. 4Mario Deile –

~ 90 % of all diffractive protons are detected

mic

rosta

tion a

t 19m

? RPs

Total TOTEM/CMS acceptance (*=1540m)

CMS+TOTEM: largest acceptance detector ever built at a hadron collider

Ro

ma

n P

ots

TOTEM+CMS

T1,T2 T1,T2

Ro

ma

n P

ots

Charged particles

Energyflux

CMS + TOTEM: AcceptancedNdN

chch/d/d

dE

/ddE

/d

p. 5Mario Deile –

T1 Telescope: Cathode Strip Chambers

• Two telescopes (forward and backward)• 5 planes of cathode strip chambers (CSC)• coverage = 2 • 3.1 < || < 4.7. • 3° rotation from plane to plane to improve pattern recognition

~3m

0.8 1.1 m• 3 projections measured

• ~350 cathode strips / detector, 5 mm pitch;

analogue read-out (CMS Buckeye chip);

resolution: x ~ 0.5 mm, y~ 0.9 mm

• ~210 anode wires / det., ( 30 m, 3 mm pitch);

digital read-out (CMS AD16 chip) provides trigger

p. 6Mario Deile –

Castor Calorimeter (CMS)

Vacuum Chamber

1800 mm400 mm

T2 Telescope: Gas Electron Multiplier

T2 GEM Telescope:• 8 planes• 5.3< ll < 6.7• 13.5 m from IP• COMPASS technology

Pads (trigger):digital readout via VFAT x = 0.06 x 0.017 2x2 mm2 7x7 mm2

Equidistant strips: analogue readout via APV2580 m wide, 400 m pitch

p. 7Mario Deile –

Proton Detectors: Roman Pots

Beampipes

Measurement of very small p scattering angles (few rad):

Leading proton detectors in RPs approach beam to 10 + 0.5 mm 1.5 mm

2004 prototype2004 prototype

p. 8Mario Deile –

Proton Detectors: What goes into the Pot?

Need full efficiency as close to the detector edge as possible;adequate resolution ~ 20 m

The edge is itself an electrode.Electrodes processed through the bulk.

SPS testbeam: Effic. transitionwithin ~15m

mm

3D Si Detectors: Planar Si with reduced current-terminating guard structure (only ~70 m):

Efficiency [a.u.]edge

p+

n+

Isurf.

Al

SPS testbeam: Effic. transition within ~60m

p. 9Mario Deile –

TOTEM Beam Optics

Reduce number of bunches (43 and 156) to avoid parasitical interactions downstream.

LTOTEM = 1.6 x 1028 cm-2 s-1 and 2.4 x 1029 cm-2 s-1

Want to measure scattering angles down to a few mrad.

Proton trajectory:

y(s) = Ly(s) y* + vy(s) y*, L(s) = [s]1/2 sin (s)

x(s) = Lx(s) x* + vx(s) x* + Dx(s) ,v(s) = [(s) ]1/2 cos (s)

• Maximise Lx(sRP), Ly(sRP) at sRP of Roman Pot

• Minimise vx(sRP), vy(sRP) at sRP of Roman Pot (parallel-to-point focussing: v = 0)

High- optics: for TOTEM = 1540 m

Consequences:

• low angular spread at IP: *) = / * 0.3 rad• large beam size at IP: * = * 0.4 mm

(if N = 1 m rad)

p. 10Mario Deile –

Running Scenarios

Scenario(goal)

1low |t| elastic,

tot , min. bias

2diffractive physics,

large pT phenomena

3intermediate |t|,

hard diffraction

4large |t| elastic

* [m] 1540 1540 200 - 400 18

N of bunches 43 156 936 2808

Half crossing angle [rad]

0 0 100 - 200 160

Transv. norm. emitt. [m rad]

1 1 3.75 3.75 3.75

N of part. per bunch

0.3 x 1011 0.6 x 1011 1.15 x 1011 1.15 x 1011 1.15 x 1011

RMS beam size at IP [m]

454 454 880 317 - 448 95

RMS beam diverg. [rad]

0.29 0.29 0.57 1.6 - 1.1 5.28

Peak luminosity

[cm-2 s-1]

1.6 x 1028 2.4 x 1029 (1 - 0.5) x 1031 3.6 x 1032

Runs at * = 0.5 m, L = (1033 1034) cm-2 s-1 not yet part of TOTEM programme but under study.

p. 11Mario Deile –

Standalone and with CMS

• Standalone running:

forseen only for elastic scattering and total cross-section.

• Common running: – DAQ and Trigger must be CMS-compatible

(hardware and software)

– TOTEM can act as a CMS subdetector.

– TOTEM can trigger CMS:

Trigger from the Roman Pots must arrive at CMS within the CMS trigger latency:

Very tight for the Pot at 220 m, but still feasible.

Pots farther than 220 m from IP (none foreseen yet) cannot trigger!

p. 12Mario Deile –

Level-1 Trigger Schemes

p

p

p

p

pT1/T2

RP RPCMS

Elastic Trigger:Signal: 500 Hz Background: 20 Hz

Single Diffractive Trigger:Signal: 200 Hz Background: < 1 Hz ? (using vertex reconstruction in T1/T2)

Double Diffractive Trigger:Signal: 100 Hz

Central Diffractive Trigger:Signal: 10 Hz Background: 2 Hz

Minimum Bias Trigger:Signal: 1 kHz

Backgrounds under study!

(L = 1.6 x 1028 cm-2 s-1)

p. 13Mario Deile –

Pomeron exchange ~ e–B|t|

diffractive structure

Photon - Pomeron interference

L dt = 1033 and 1037 cm-2

pQCD ~ |t|–8

Elastic Scattering Cross-Section

p. 14Mario Deile –

Coulomb region 510-4 [lower s, RP closer to beam]Interference, meas. 510-4 510-3 [as above], standard * = 1540 mPomeron exchange 510-3 0.1 * = 1540 mDiffractive structure 0.1 1 * = 1540 m, 18 mLarge |t| – perturb. QCD 1 10 * = 18 m

Region |t| [GeV]2 Running Scenario

Elastic Scattering: t-Acceptance

p. 15Mario Deile –

Elastic Scattering: Resolution

t-resolution (2-arm measurement) -resolution (1-arm measurement)

Test collinearity of particles in the 2 arms Background reduction.

p. 16Mario Deile –

• Current models predictions: 100-130mb

• Aim of TOTEM: ~1% accuracy

Total p-p Cross-Section

mb 1.41.2

2.1 5.111 tot 0058.0

0025.0 .00150 1361.0 LHC:

TE

VA

TR

ON

ISR

UA

4 UA

5

LH

C

Cosmic Rays

COMPETE Collaboration fits:

Ps

sB

s

ss

Yss

Ypppp

tot

2

0

11)( ln

[PRL 89 201801 (2002)]

p. 17Mario Deile –

Measurement of tot

Luminosity-independent measurement of the total cross-section using the Optical Theorem:

02

2

1

16

t

eltot dt

dN

L

ineleltot NN L inelel

teltot NN

dtdN

0

2

)/(

1

16

• Measure the elastic and inelastic rate with a precision better than 1%.• Extrapolate the elastic cross-section to t = 0.

Or conversely:Extract luminosity:

0

22

|/16

1

tel

inelel

dtdN

NN

L

p. 18Mario Deile –

Extrapolation of Elastic Cross-Section to t = 0

Effect Extrapolation uncertainty

Statistics (10h @ 1028): 107 events 0.07 %

Uncertain functional form of d/dt

0.5 %

Beam energy uncertainty 0.05 % 0.1 %

Beam / detector offset 20 m 0.08 %

Crossing angle 0.2 rad 0.1 %

Total 0.53 %

Non-exponential d/dt fitted to

Slope parameter

according to BSW Model

tBftf e)( 0

dtdf

tftB

1

p. 19Mario Deile –

Measurement of the Total Rate Nel + Ninel

[mb]

T1/T2 double arm trigger loss

[mb]

T1/T2 single arm

trigger loss [mb]

Uncertainty after extrapolation

[mb]

Minimum bias 58 0.3 0.06 0.06

Single diffractive 14 - 2.5 0.6

Double diffractive 7 2.8 0.3 0.1

Double Pomeron 1 ~ 0.2

(using leading p and CMS)

0.02

Elastic Scattering 30 - - 0.15

Acceptancesingle diffraction

simulated

extrapolateddetectedLoss at low

masses

Extrapolation of diffractive cross-section to large 1/M2 using d/dM2 ~ 1/M2 .

Total: 0.8 %

p. 20Mario Deile –

Accuracy of tot

%1005.0008.0005.0 222 tot

tot

Extrapolation to t = 0 Total rate Nel + Ninel = 0.12 ± 0.02

p. 21Mario Deile –

~ 90 % of all diffractive protons are seen in the Roman Pots(assuming ).

= p / p can be measured with a resolution of ~ 5 x 10-3 .

Diffraction at high Acceptance

A < 5 %

A > 95 %

85 - 95 %

* = 1540 m

t

dtd

d 10e1

p. 22Mario Deile –

y = – ln

ymax = 6.5

Trigger via Roman Pots > 2.5 x 10-2

Trigger via rapidity gap < 2.5 x 10-2

* = 1540 m: = 0.5% L 2.4 x 1029 cm-2 s-1

* = 200 400 m: ~ 1 ‰ L 1031 cm-2 s-1

* = 0.5 m: ~ 1 ‰ L > 1031 cm-2 s-1

Detection Prospects for Double Pomeron Events

In collaboration with CMS

dN/dy

– ln – ln

y

pp

CMS

CMS + TOTEM

p1

p2 p2’

p1’

PM2 = s

P

* = 0.5 m

p. 23Mario Deile –

Exclusive Production by DPE: Examples

Advantage: Selection rules: JP = 0+, 2+, 4+; C = +1 reduced background, determination of quantum numbers.Good resolution in TOTEM: determine parity: P = (-1)J+1 d/d~ 1 +– cos 2

Particle excl Decay channel BRRate at

2x1029 cm-2 s-1

Rate at

1031 cm-2 s-1

(no acceptance / analysis cuts)

c0

(3.4 GeV)3 b [KMRS]

J/ +–

+ – K+ K–

6 x 10-4

0.018

1.5 / h

46 / h

62 / h

1900 / h

b0

(9.9 GeV)4 nb [KMRS] +– 10-3 0.07 / d 3 / d

H

(120 GeV)

0.1 100 fb

assume 3 fbbb 0.68 0.02 / y 1 / y

Higgs needs L ~ 1033 cm-2 s-1, i.e. a running scenario for = 0.5 m:• try to modify optics for enhanced dispersion,• try to move detectors closer to the beam,• install additional Roman Pots in cold LHC region at a later stage.

p. 24Mario Deile –

Status and Outlook

• TDR was submitted to the LHCC in January • Extensive test-beam programme in summer/autumn

• A TDR on the common CMS/TOTEM physics programme will be submitted in early 2005

p. 25Mario Deile –

p. 26Mario Deile –

GEMs at high luminosities

Test results from COMPASS, HERA-B and LHCb have shown: Rate:

Exposed to 350 MeV π+, π– and p beam (~ 105 / mm2 s) at PSIi.e. rates expected in T2 at L=1033 cm-2 s-1 (incl. background)

Ageing:tests at high rate: no sign of ageing observed after 7 mC / mm2 (equiv. 1011 mip / mm2 or 1 year (107 s) at L=1032 cm-2 s-1)

Time resolution:12.5 ns with Ar/CO2 easily identifies bunches with 75 ns spacing

Sparking:Spark probability measured to be very low at gains of ~104 ,no damage after 5000 sparks

The detector technology is proven and well adapted to the requirements for the T2telescope up to 1033 cm-2 s-1 luminosity.Problem: radiation hardness of the electronics to be tested.

p. 27Mario Deile –

L(s)

High Optics: Lattice Functions

Ly

Lx

vx

vy

v(s)

Parallel-to-point focussing achieved at 220 m (RP station 3) for both x and y !

p. 28Mario Deile –

Dominant background: beam halo: reduction only by 2-arm coincidence.

T1/T2: beam-gas suppression by vertex reconstruction: (r) = 3 mm, (z) = 45 mm

Trigger Logic and Background SuppressionEach Roman Pot houses:• 6 tracking planes (analogue APV 25 readout)• 4 trigger planes (digital VFAT readout)

p. 29Mario Deile –

Diffraction at high Acceptance (2)