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Forward Physics with the TOTEM  CMS at the LHC Risto Orava. Forward physics at the LHC Signature studies Experimental layout An example: pp p+H+p Outlook. XIII ISVHECRI Pylos, Greece, 6-12 September 2004 R.Orava.

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Forward Physics with the

TOTEMCMS at the LHC

Risto Orava

  • Forward physics at the LHC

  • Signature studies

  • Experimental layout

  • An example: ppp+H+p

  • Outlook

XIII ISVHECRI Pylos, Greece, 6-12 September 2004 R.Orava

Low-x Workshop, Prague 17 September 2004 Risto Orava


The Large Hadron Collider (LHC)

pp collisions at 14 TeV

LHC is built into

27 km the LEP tunnel

  • 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 events

    per bunch crossing

CMS/TOTEM

ALICE

LHC-B

ATLAS

Planned Startup on Spring 2007


Total TOTEM/CMS acceptance (b*=1540m)

RPs

microstation at 19m?

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.

Charge flow

information value low:

- bulk of the particles crated late

in space-time

leading protons

leading protons

Energy flow

information value high:

- leading particles created early

in space-time

TOTEM + CMS

In the forward region (|h > 5): few particles with large energies/small

transverse momenta.


Diffractive Scattering has distinctive signatures

‘wee’ partons  lns

Elastic

soft

SDE

hard

SDE

hard

CD

s-channel view

p

jet

lnMX2

Baryonic charge distribution

r  0.4fm

jet

Valence quarks in a bag with

r  0.1fm

lns

h

Rapidity gap

survival & ”underlying”

event structures are

intimately connected

with a geometrical

view of the scattering

- eikonal approach!

p

Soft diffractive scattering

Hard diffractive scattering

’Glansing’ scattering of proton fields

R.Orava


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

Min-Bias

Min-Bias

  • 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

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

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


Photon - Pomeron interferencer

Pomeron exchange (~exp Bt)

diffractive structure

pQCD

Ldt = 1033 & 1037 cm2

Studying elastic scattering an soft diffraction requires

special LHC optics. These will yield large statistics.

ds/dt (mb/GeV2)

high-t

(* = 1540 m & 18 m)


Diffractive Cross Sections are Large

Rel = sel(s)/stot(s)

Rdiff = [sel(s) + sSD(s) + sDD(s)]/stot(s)

0.30

0.375

  • sel  30% of stot at the LHC ?

  • sSD + sDD  10% of stot (= 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

simulated

extrapolated

Acceptance

Loss at low masses

detected


TOTEM will measure stot to 1%

TOTEM


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

  • Investigate QCD:stot, 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 (pp3jets+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 gg-mode.)

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

  • Luminosity measurement with DL/L 5 %


As a Gluon Factory LHC could deliver... physics program at the LHC

  • 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 & t+t- 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 ggpairs, extra dimensions


longer Q physics program at the LHC2

extrapolation

smaller x

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

J. Stirling


Relative precision on the measurement of physics program at the LHCHBR 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)

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

Luminosity relates the cross sectionsof a given process by:

L = N/s

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

Measure simultaneously elastic (Nel) & inelastic rates (Ninel), extrapolateds/dt  0, assumer-parameter to be known:

(1+r2) (Nel + Ninel)2

L =

16p dNel/dt|t=0

Ninel = ?  Need a hermetic detector.

dNel/dtt=0 = ?  Minimal extrapolation to t0: tmin 0.01


Forward Physics Scenarios physics program at the LHC

Proton

b* (m)

rapidity

gap

L(cm-2s-1)

inelastic

activity

jet

g,e,m,t

L, D++,...

TOTEM

& CMS

TOTEM

& CMS

TOTEM

& CMS

elastic scattering

1540

18

beam halo?

1028 -1032

total cross section

inelastic

acceptance

1540

1028 -1033

soft diffraction

1540

200-400

gap

survival

L, K±,

,...

1029 -1031

mini-jets?

200-400

0.5

jet

acceptance

central

& fwd

W, Z,

J/,...

hard diffraction

1031 -1033

200-400

0.5

di-jet

backgr

central

pair

b-tag, g,

J/,...

DPE Higgs, SUSY,...

1031 -1033

trigger

200-400

0.5

mini-jets

resolved?

central

& fwd jets

di-leptons

jet-g,...

low-x physics

1031 -1033

exotics (DCC,...)

p± vs. po

multiplicity

jet

anomalies?

leptons

g’s,...?

0.5

1031 -1033

R.Orava


Correlation with the CMS Signatures physics program at the LHC

  • e, g, m, t, and b-jets:

    • tracking: |h| < 2.5

    • calorimetry with fine granularity: |h| < 2.5

    • muon: |h| < 2.5

  • Jets, ETmiss

    • calorimetry extension: |h| < 5

  • High pT Objects

    • Higgs, SUSY,...

  • Precision physics (cross sections...)

    • energy scale: e & m 0.1%, jets 1%

    • absolute luminosity vs. parton-parton luminosity via

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

R.Orava


To Reach the Forward Physics Goals We Need: physics program at the LHC

  • Leading Protons

  • Extended Coverage of Inelastic Activity

  • CMS


Need to Measure Inelastic Activity and Leading Protons physics program at the LHC

over Extended Acceptance in , ,  and –t.

Measurement stations (Roman Pots) at locations optimized

vs. the LHC beam optics. Both sides of the IP.

LP1

LP2

LP3

147 m

180 m

220 m

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 by

beam energy spread (large ).

For Higgs, SUSY etc. heavier states need LP4,5 at 300-400m!


TOTEM ROMAN POT IN CERN TEST BEAM physics program at the LHC


Microstation – Next Generation Roman Pot physics program at the LHC

-station concept

(Helsinki proposal)

Silicon pixel detectors in

vacuum (shielded)

Very compact

A solution for 19m, 380 & 420m?

Movable detector


Diffraction at high physics program at the LHCb*: Acceptance

Luminosity 1028-1030cm-2s-1 (few days or weeks)

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

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


CMS tracking is extended by forward telescopes physics program at the LHC

on both sides of the IP

CMS

T1-CSC: 3.1 < h < 4.7

T2-GEM: 5.3 <h< 6.5

T3-MS: 7.0 <h< 8.5 ?

T1

T2

10.5 m

CASTOR

~14 m

T3?

~19 m

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


Running Scenarios 1: High & Intemediate physics program at the LHCb*

- low b* physics will follow...


The process: pp physics program at the LHC p + H + p

h

p

10

p1

p’

Dh

5

b-jet

0++

q1

b

-

H

0

q2

b

0++

-

b-jet

-5

Dh

p2

p”

-10

p

MH2 = (p1 + p2 – p’ – p”)2  x1x2s (at the limit, where pT’ & pT” are small)

x1 = 1-p’q1/p1q1  1-p’/p1x2 = 1-p”q2/p2q2  1-p”/p2


Leading proton studies at low physics program at the LHC*

  • GOAL: New particle states in Exclusive DPE

  • L > few 10 32 cm2 s1 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 cm2 s1

  • Pair of leading protons  central mass resolution  background

  • rejection

A study by the Helsinki group in TOTEM.


Central Diffraction produces two leading protons, physics program at the LHC

two rapidity gaps and a central hadronic system. In the

exclusive process, the background is suppressed and the

central system has selected quantum numbers.

Survival of the rapidity gaps?1

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

MX212s

Measure the parity P = (-1)J:

ds/d 1 + cos2

2p

Gap

Jet+Jet

Gap

0

hmin

h

hmax

Mass resolution  S/B-ratio

R.Orava

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


The Experimental Signatures: physics program at the LHC

pp  p + X + p

- vertex position in the transverse plane?

b-jet

Detector

Detector

CMS

p2’

p1’

_

-

b-jet

- resolution in x ?

-beam energy spread?

Aim at measuring the:

  • Leading protons on both sides down to D  1‰

  • - Rapidity gaps on both sides – forward activity – for |h| > 5

  • Central activity in CMS


Leading Proton Detection physics program at the LHC

0m

147m

180m

220m

308m

338m

420 430m

D2

Q4

Q5

Q6

Q7

B8

Q8

B9

Q9

B10

Q10

B11

IP

D1

Q1-3

x = 0.02

Jerry & Risto


Mass Acceptance physics program at the LHC

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.

All

pp p + X + p

308 m

420 m

MX = 120 GeV

e 45%

All detectors

combined

MX = 60 GeV

e 30%

308m

e 15%

420m

MX (GeV)


Momentum loss resolution at 420 m physics program at the LHC

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


DPE Mass Measurement at 400m physics program at the LHC

Gaussian s(M) vs. central mass

assuming DxF/xF = 10-4

s(M) = (1.5 - 3.0) GeV (DxF/xF = (1-2)10-4)

s(M) (GeV)

  • Note: s(M)/M = 1.1% s(M) = 1.3 GeV - Gaussian width

  • To contain 87% of the signal need 3xs(M) = 3.9 GeV

symmetric case:

 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)

Central Mass (GeV)

Helsinki group/J.Lamsa & R.O.


SUMMARY: physics program at the LHC

TOTEM opens up Forward Physics to the LHC

TOTEMCMS 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


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