Forward Physics with the TOTEMCMS at the LHC

Risto Orava

XIII ISVHECRI Pylos, Greece, 6-12 September 2004 R.OravaLow-x Workshop, Prague 17 September 2004 Risto Orava

• Forward physics at the LHC• Signature studies• Experimental layout• An example: ppp+H+p• Outlook

CMS/TOTEM

The Large Hadron Collider (LHC)

ATLAS

ALICE

LHC-B

LHC is built into 27 km the LEP tunnel

pp collisions at 14 TeV

5 experiments

25 ns bunch spacing 2835 bunches 1011 p/bunch

Design Luminosity:1033cm-2s-1 -1034cm-2s-1

100 fb-1/year

23 inelastic eventsper bunch crossing

Planned Startup on Spring 2007

Important part of the phase space is not covered by the generic designs at LHC. TOTEM CMS Covers more than any previous experiment at a hadron collider.

In the forward region (| > 5): few particles with large energies/small transverse momenta.

Charge flow

Energy flow

information value low: - bulk of the particles crated late in space-time

information value high: - leading particles created early in space-time

mic

rosta

tion a

t 19m

?

RPs

Total TOTEM/CMS acceptance (*=1540m)

TOTEM + CMS

lead

ing

pro

ton

s

lead

ing

pro

ton

s

Diffractive Scattering has distinctive signatures

Soft diffractive scattering

Hard diffractive scattering

Valence quarks in a bag with

r 0.1fm

Baryonic charge distribution

r 0.4fm

‘wee’ partons lns

Rapidity gapsurvival & ”underlying”event structures areintimately connectedwith a geometricalview of the scattering- eikonal approach!R.Orava

s-channel view

p

p

lns

lnMX2

jet

jet

Elastic soft SDE

hard SDE

hard CD

’Glansing’ scattering of proton fields

How to manage with the high-pT signatures in the environment of an underlying event?

Proton AntiProton

“Soft” Collision (no hard scattering)

Proton AntiProton

“Hard” Scattering

PT(hard)

Outgoing Parton

Outgoing Parton

Underlying Event Underlying Event

Initial-State Radiation

Final-State Radiation

Proton AntiProton

“Underlying Event”

Beam-Beam Remnants Beam-Beam Remnants

Initial-State Radiation

Unavoidable background to be removed from the jets before comparing to NLO QCD predictions

LHC: most of collisions are “soft’’, outgoing particles roughly in the same direction as the initial protons.

Occasional “hard’’ interaction results in large transverse momentum outgoing partons.

The “Underlying Event’’ is everything but the two outgoing Jets, including :

initial/final gluon radiation beam-beam remnants secondary semi-hard interactions

Min-Min-BiasBiasMin-Bias

How do we control the kinematics (DIS vs. hh)?

L dt = 1033 & 1037 cm2

Pomeron exchange (~exp Bt)

diffractive structure

pQCD

Photon - Pomeron interference

(* = 1540 m & 18 m)

d/

dt

(mb

/GeV

2)

Studying elastic scattering an soft diffraction requires special LHC optics. These will yield large statistics.

high-t

Diffractive Cross Sections are Large

0.375

Rel = el(s)/tot(s) Rdiff = [el(s) + SD(s) + DD(s)]/tot(s)

0.30

el 30% of tot at the LHC ? SD + DD 10% of tot (= 100-150mb) at the LHC ?

Inelastic rates are uncertain in the forward region

Event selection:• trigger from T1 or T2 (double arm o single arm)• Vertex reconstruction (to eliminate beam-gas bkg.)

Extrapolation for diffractive events needed

Lost events

Acceptance

simulated

extrapolated

detectedLoss at low masses

TOTEM will measure tot to 1%

TOTEM

Additional forward coverage opens up new complementary physics program at the LHC

• Investigate QCD: tot, elastic scattering, soft & hard diffraction, multi- rapidity gap events (see: Hera, Tevatron, RHIC...) - confinement.– Studies with pure gluon jets: gg/qq… - LHC as a gluon factory!

– Gluon density at small xBj (10-6 – 10-7) – “hot spots” of glue in vacuum?

– Gap survival dynamics, proton parton configurations (pp3jets+p) – underlying event structures

– Diffractive structure: Production of jets, W, J/, b, t, hard photons,– Parton saturation, BFKL dynamics, proton structure, multi-parton

scattering• Search for signals of new physics based on forward protons + rapidity gaps

Threshold scan for JPC = 0++ states in: pp p+X+p – spin-parity of X! (LHC as the e+e- linear collider in -mode.)

• Extension of the ‘standard’ physics reach of the CMS experiment into the forward region

• Luminosity measurement with L/L 5 %

0 0c bχ , χ

As a Gluon Factory LHC could deliver...

• О(100k) high purity (q/g = 1/3000) gluon jets with ET > 50 GeV in 1 year; gg-events as “Pomeron-Pomeron” luminosity monitor

• Possible new resonant states, e.g. Higgs (О(100) H bb events per year with mH = 120 GeV, L=1034)*, glueballs, quarkonia 0++ (b ), gluinoballs - complementary to inclusive analyses (bb, WW & decays)

• Invisible decay modes of Higgs (and SUSY)?!• CP-odd Higgs

• Squark & gluino thresholds well separated - practically background free signature: multi-jets & ET

- model independence (missing mass!) [expect O(10) events for gluino/squark masses of 250 GeV]

- an interesting scenario: gluino as the LSP with mass window 25-35 GeV(S.Raby)

• O(10) events with isolated high mass pairs, extra dimensions

gg

10-7

10-6

10-5

10-4

10-3

10-2

10-1

100

100

101

102

103

104

105

106

107

108

109

fixedtarget

HERA

x1,2

= (M/1.96 TeV) exp(y)Q = M

Tevatron parton kinematics

M = 10 GeV

M = 100 GeV

M = 1 TeV

422 04y =

Q2

(GeV

2 )

x

10-7

10-6

10-5

10-4

10-3

10-2

10-1

100

100

101

102

103

104

105

106

107

108

109

fixedtarget

HERA

x1,2

= (M/14 TeV) exp(y)Q = M

LHC parton kinematics

M = 10 GeV

M = 100 GeV

M = 1 TeV

M = 10 TeV

66y = 40 224Q

2 (G

eV2 )

x

longer Q2

extrapolation

smaller x

J. Stirling

Low-x Physics at the LHCGain in x-reach & Q2-range

In addition: The signatures of new physics have to be normalized: The Luminosity Measurement

Luminosity relates the cross section of a given process by:L = N/

A process with well known, calculable and large (monitoring!) with a well defined signature? Need complementarity.

Measure simultaneously elastic (Nel) & inelastic rates (Ninel), extrapolate d/dt 0, assume -parameter to be known:

(1+2) (Nel + Ninel)2

16dNel/dt|t=0

L =

Ninel = ? Need a hermetic detector.

dNel/dtt=0 = ? Minimal extrapolation to t0: tmin 0.01

Relative precision on the measurement of HBR for various channels, as function of mH, at Ldt = 300 fb–1. The dominant uncertainty is from Luminosity: 10% (open symbols), 5% (solid symbols).

(ATL-TDR-15, May 1999)

Forward Physics ScenariosProton

* (m)

rapiditygap L(cm-2s-1)

jetinelasticactivity

,e,, , ++,...

elastic scattering

total cross section

soft diffraction

hard diffraction

1540 18

1540

1540200-400

200-400 0.5

low-x physics

exotics (DCC,...)

DPE Higgs, SUSY,...central pair

central & fwd

inelasticacceptance gap survival

jetacceptance di-jet backgr

b-tag, ,J/,...

1028 -1032

1029 -1031

1028 -1033

1031 -1033

1031 -1033

TOTEM& CMS

TOTEM& CMS

TOTEM& CMS

central& fwd jets

di-leptonsjet-

mini-jetsresolved?

± vs. o

multiplicity

leptons’s

jetanomalies?

W, Z, J/,...

, K±,,...

0.5

1031 -1033

1031 -1033

200-400 0.5

200-400 0.5

mini-jets?

R.Orava

beam halo?

trigger

Correlation with the CMS Signatures

• e, , , , and b-jets:• tracking: || < 2.5• calorimetry with fine granularity: || < 2.5• muon: || < 2.5

• Jets, ETmiss

• calorimetry extension: || < 5

• High pT Objects• Higgs, SUSY,...

• Precision physics (cross sections...)• energy scale: e & 0.1%, jets 1% • absolute luminosity vs. parton-parton luminosity via

”well known” processes such as W/Z production?

R.Orava

• Leading Protons

• Extended Coverage of Inelastic Activity

• CMS

To Reach the Forward Physics Goals We Need:

Need to Measure Inelastic Activity and Leading Protons over Extended Acceptance in , , and –t. Measurement stations (Roman Pots) at locations optimized vs. the LHC beam optics. Both sides of the IP.

147 m147 m 180 m180 m 220 m220 m

LP1LP1 LP2LP2 LP3LP3

Measure the deviation of the leading proton location from the nominal beam axis () and the angle between the two measurement locations (-t) within a doublet.Acceptance is limited by the distance of a detector to the beam.Resolution is limited by the transverse vx location (small ) and bybeam energy spread (large ).For Higgs, SUSY etc. heavier states need LP4,5 at 300-400m!

TOTEM ROMAN POT IN CERN TEST BEAM

Microstation – Next Generation Roman Pot

-station concept (Helsinki proposal)

Silicon pixel detectors in vacuum (shielded)

Movable detector

Very compactA solution for 19m, 380 & 420m?

• more than 90% of all diffractive protons are seen!

• proton momentum can be measured with a resolution of few 10-3

Diffraction at high *: AcceptanceLuminosity 1028-1030cm-2s-1 (few days or weeks)

~14 m

CMSCMS T1-CSC: 3.1 < < 4.7

T2-GEM: 5.3 < < 6.5

T3-MS: 7.0 < < 8.5 ?

10.5 mT1T1 T2T2

T3?T3?

CMS tracking is extended by forward telescopes on both sides of the IP

~19 m

- A microstation (T3) at 19m is an option.

CASTORCASTOR

Running Scenarios 1: High & Intemediate *

Scenario(goal)

1low |t| elastic,tot , min. bias

2diffr. phys.,

large pT phen.

3intermediate |

t|, hard diffract.

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 luminos. [cm-2 s-1]

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

- low * physics will follow...

The process: pp p + H + p

p

p

b-jet

b-jet

p1

p2

p’

p”

b

b0

5

-5

10

-10

-

-0++

H

MH2 = (p1 + p2 – p’ – p”)2 12s (at the limit, where pT’ & pT” are small)

1 =p’q1/p1q1 1-p’/p1 2 = 1-p”q2/p2q2 1-p”/p2

0++

q1

q2

Leading proton studies at low *

GOAL: New particle states in Exclusive DPE

• L > few 10 32 cm2 s1 for cross sections of ~ fb (like Higgs)

• Measure both protons to reduce background from inclusive

• Measure jets in central detector to reduce gg background

Challenges:

• M 100 GeV need acceptance down to ’s of a few ‰

• Pile-up events tend to destroy rapidity gaps L < few 10 33 cm2 s1

• Pair of leading protons central mass resolution background

rejection

A study by the Helsinki group in TOTEM.

Central Diffraction produces two leading protons, two rapidity gaps and a central hadronic system. In the exclusive process, the background is suppressed and the central system has selected quantum numbers.

JPC = 0++ (2++, 4++,...)

Gap GapJet+Jet

min max

Survival of the rapidity gaps?1

1 V.A.Khoze,A.D.Martin and M.G.Ryskin, hep-ph/0007359R.Orava

Measure the parity P = (-1)J:d/d 1 + cos2

Mass resolution S/B-ratio

MX212s

The Experimental Signatures: pp p + X + p

b-jet

CMS

- Leading protons on both sides down to 1‰- Rapidity gaps on both sides – forward activity – for || > 5- Central activity in CMS

- resolution in ?-beam energy spread?

- vertex position in the transverse plane?

-

Aim at measuring the:

Detector Detector

p2’ p1’

b-jet_

Leading Proton Detection 147m 180m 220m0m 308m 338m 420 430m

IP

Q1-3

D1

D2 Q4 Q5 Q6 Q7 B8 Q8 B9 Q9 B10 B11Q10

Jerry & Risto

= 0.02

Mass Acceptance

Both protons are seen with 45 % efficiency at MX = 120 GeV

Some acceptance down to: MX = 60 GeV

308m & 420m locations select symmetric proton pairs acceptance decreases.

308 m420 m

pp p + X + p

MX (GeV)

MX = 60 GeV

MX = 120 GeV

All

45%

30%

15%

All detectors combined

308m

420m

Resolution improves with increasing momentum loss

Dominant effect: transverse vertex position (at small momentum loss) and beam energy spread (at large momentum loss, 420 m)/detector resolution (at large momentum loss, 215 m & 308/338 m)

proton momentum loss

proton momentum loss

Momentum loss resolution at 420 m

DPE Mass Measurement at 400m

Gaussian (M) vs. central massassuming xF/xF = 10-4

symmetric case:

Central Mass (GeV)

(M

) (G

eV

)

= (1.5 - 3.0) GeV (xF/xF = (1-2)10-

4)

65% of the data

20 GeV < MX < 160 GeV

(MXmax determined by the aperture of the last dipole,B11, MXmin by the minimum deflection = 5mm)

Helsinki group/J.Lamsa & R.O.

Note: (M)/M = 1.1% (M) = 1.3 GeV - Gaussian width- To contain 87% of the signal need 3x(M) = 3.9 GeV

SUMMARY:TOTEM opens up Forward Physics to the LHC

TOTEMCMS covers more phase space than any previous experiment at a hadron collider.

Fundamental precision measurements on elastic scattering, total cross section and QCD:• non-perturbative structure of proton• studies of pure gluon jets – LHC as a gluon factory• gluon densities at very small xBj…• parton configurations in proton

Searches for signals of new physics:• Threshold scan of 0++ states in exclusive central diffraction: Higgs, SUSY (mass resolution crucial for background rejection)

Extension of the ‘standard’ physics reach of CMS into the fwd region & Precise luminosity measurement