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Forward Proton Tagging at the LHC as a Tool to Study New Physics

V.A. Khoze (IPPP, Durham)

main aims to illustrate the theoretical motivations behind the recent proposals to add the Forward Proton Taggers to the LHC experiments.

to show that the Central Exclusive Diffractive Processes may provide an exceptionally clean environment to search for and to identify the nature of new objects at the LHC

FP-420

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1. Introduction (gluonic Aladdin’s lamp)

2.Basic elements of KMR approach (qualitative guide)

3. Prospects for CED Higgs production. the SM case MSSM Higgs sector ( troublesome regions) MSSM with CP-violation.

4.‘Exotics’

5. The ‘standard candle’ processes.( experimental checks)

6. Conclusion

7. Ten commandments of Physics with Forward Protons at the LHC .

PLAN

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CMS & ATLAS were designed and optimised to look beyond the SM

High -pt signatures in the central region

But… ‘incomplete’

• Main physics ‘goes Forward’

•Difficult background conditions.

• The precision measurements are limited by systematics (luminosity goal of δL ≤5%)

Lack of :

•Threshold scanning , resolution of nearly degenerate states (e.g. MSSM Higgs sector)•Quantum number analysing

ILC chartered territory•Handle on CP-violating effects in the Higgs sector•Photon – photon reactions

Is there a way out?

☺ YES-> Forward Proton Tagging

Rapidity Gaps Hadron Free Zones

matching Δ Mx ~ δM (Missing Mass)

RG

RG

X

p

p p

p

talk by A. De Roeck

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Forward Proton Taggers as a gluonic Aladdin’s Lamp (Old and New Physics menu)

•Higgs Hunting (the LHC ‘core business’) K(KMR)S- 97-04

•Photon-Photon, Photon - Hadron Physics

• ‘Threshold Scan’: ‘Light’ SUSY … KMR-02 • Various aspects of Diffractive Physics (soft & hard ). KMR-01

(strong interest from cosmic rays people ) High intensity Gluon Factory (underrated gluons) KMR-00, KMR-01 QCD test reactions, dijet P-luminosity monitor

•Luminometry KMOR-01

•Searches for new heavy gluophilic states KMR-02, KMRS-04

FPTWould provide a unique additional tool to complement the conventional strategies at the LHC and ILC.

Higgs is only a part of the broad EW, BSM and diffractive program@LHC wealth of QCD studies, glue-glue collider, photon-hadron, photon-photon interactions…

FPT will open up an additional rich physics menu ILC@LHC

Albert De Roeck

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The basic ingredients of the KMR

approach (Khoze-Martin-Ryskin 1997-2006)

Interplay between the soft and hard dynamics

Bialas-Landshoff- 91 rescattering/absorptive ( Born -level ) effects

Main requirements:•inelastically scattered protons remain intact

•active gluons do not radiate in the course of evolution up to the scale M

•<Qt> >>/\QCD in order to go by pQCD book(CDPE) ~ 10 * (incl)

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RG signature for Higgs hunting (Dokshitzer, Khoze, Troyan, 1987). Developed and promoted by Bjorken (1992-93)

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(CDPE) ~ 10 * incl-4

How would you explain it to your (grand) children ?

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Forcing two (inflatable) camels to go through the eye of a needle

High price to pay for such a clean environment:

σ (CEDP) ~ 10-4 σ( inclus.)

Rapidity Gaps should survive hostile hadronic radiationdamages and ‘partonic pile-up ‘

W = S² T²Colour charges of the ‘digluon dipole’ are screened

only at rd ≥ 1/ (Qt)ch

GAP Keepers (Survival Factors) , protecting RG against:

the debris of QCD radiation with 1/Qt≥ ≥ 1/M (T)

soft rescattering effects (necessitated by unitariy) (S)

HP P

How would you explain it to your (grand) children ?

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Reliability of predn of (pp p + H + p) crucial

contain Sudakov factor Tg which exponentiallysuppresses infrared Qt region pQCD

S2 is the prob. that the rapidity gaps survive population by secondary hadrons soft physics S2=0.026 (LHC) S2=0.05 (Tevatron)

(pp p + H + p) ~ 3 fb at LHC for SM 120 GeV Higgs ~0.2 fb at Tevatron

H

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Possible role of semi-enhanced hard rescattering corrections

J. Bartels et al (hep-ph/0601128)

KMR (hep-ph/0602247) Enhanced corrections should be smallat LHC energies.

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pp ‘New Heavy’ States M

(S²)γγ =0.86 (KMR-

02)

αs²/8

we should not underestimate photon fusion !

T²

²

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Highlights:• CM energy W up to/beyond 1 TeV (and under control) • Large photon flux F therefore significant luminosity• Complementary (and clean) physics to pp interactions, eg studies of exclusive production of heavy particles might be possible opens new field of studying very high energy (and p) physics

LHC as a High Energy Collider

pp

K. Piotrzkowski, Phys. Rev. D63 (2001) 071502(R)J.Ohnemus, T.Walsh & P .Zerwas -94;

KMR-02

Very rich Physics Menu

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Higgs boson

REWARD 2.5 billion

LHC cost

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Current consensus on the LHC Higgs search prospects

•SM Higgs : detection is in principle guaranteed for any mass. ☺

•In the MSSM h-boson most probably cannot escape detection, and in

large areas of parameter space other Higgses can be found. ☺

•But there are still troublesome areas of the parameter space: intense coupling regime of MSSM, MSSM with CP-violation…..

•More surprises may arise in other SUSYnon-minimal extensions: NMSSM……

• After discovery stage (Higgs Identification):

The ambitious program of precise measurements of the Higgs mass, width, couplings, and, especially of the quantum numbers and CP properties would require an interplay with a ILC

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The advantages of CED Higgs production

• Prospects for high accuracy mass measurements irrespectively of the decay mode. ( H-width and even missing mass lineshape in some BSM scenarios).

• Valuable quantum number filter/analyzer. ( 0++ dominance ;C , P-even)

difficult or even impossible to explore the light Higgs CP at the LHC conventionally.

(selection rule - an important ingredient of pQCD approach,

• H ->bb ‘readily’ available

(gg)CED bb LO (NLO,NNLO) BG’s -> studied

SM Higgs S/B~3(1GeV/M) complimentary information to the conventional studies.

• For some (troublesome) areas of the MSSM parameter space may become a discovery channel

• H →WW*/WW - an added value especially for SM Higgs with M≥ 135GeV,

- ‘an advantageous investment’

• New run of the MSSM studies is underway (with G. Weiglein et al)

• New leverage –proton momentum correlations

(probes of QCD dynamics, pseudoscalar ID , CP- violation effects) KMR-02; J.Ellis et al -05

LHC : ‘after discovery stage’, Higgs ID……

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☻Experimental Advantages

– Measure the Higgs mass via the missing mass technique

Mass measurements do not involve Higgs decay products

Experimental Challenges

– Tagging the leading protons– Selection of exclusive events & backgrounds– Triggering at L1 in the LHC experiments

– Model dependence of predictions:

(soft hadronic physics is involved after all)

– resolve many of the issues with Tevatron data

There is still a lot to learn from present and future Tevatron diffractive data (KMRS- friendly so far).

Albert De Roeck

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H

b jets : MH = 120 GeV s = 2 fb (uncertainty factor ~2.5)

MH = 140 GeV s = 0.7 fb

MH = 120 GeV : 10 signal / O(10) background in 30 fb-1

WW* : MH = 120 GeV s = 0.4 fb

MH = 140 GeV s = 1 fb

MH = 140 GeV : 5-6 signal / O(3) background in 30 fb-1

•The b jet channel is possible, with a good understanding of detectors and clever level 1 trigger ( μ-trigger from the central detector at L1 or/and RP(220) +jet condition)

•The WW channel is extremely promising : no trigger problems, better mass resolution at higher masses (even in leptonic / semi-leptonic channel), weaker dependence on jet finding algorithms

•The mode looks advantageous

If we see SM-like Higgs + p- tags the quantum numbers are 0++

Exclusive SM Higgs production

(with detector cuts)

(with detector cuts)

H

optimistically

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The MSSM and more exotic scenarios

If the coupling of the Higgs-like object to gluons is large, double proton tagging becomes very attractive

• The intense coupling regime of the MSSM

(E.Boos et al, 02-03)

• CP-violating MSSM Higgs physics (A.Pilaftsis,98; M.Carena et al.,00-03, B.Cox et al 03, KMR-03, J. Ellis et al -05)

Potentially of great importance for electroweak baryogenesis

• an ‘Invisible’ Higgs (BKMR-04)

• NMSSM ( with J. Gunion )

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Theoretical Input

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(h SM-like, H/A- degenerate.)

21(theoretical expectations –more on the conservative side)

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The intense coupling regime is where the masses of the 3 neutral Higgs bosons are

close to each other and tan is large suppressed

enhanced

0++ selection rule suppresses A production:

CEDP ‘filters out’ pseudoscalar production, leaving pure H sample for studyMA = 130 GeV, tan = 50

Mh = 124 GeV :71signal / (3-9) background in 30 fb-1

MH = 135 GeV : 124 signal / (2-6) background in 30 fb-1

MA = 130 GeV : 3 signal / (2-6) background in 30 fb-1

Well known difficult region for conventional channels, tagged proton channel may well be the discovery channel , and is certainly a powerful spin/parity filter

The MSSM can be very proton tagging friendly

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decoupling regime

mA ~ mH 150GeV,tan >10;

h = SM

intense coupl:mh ~ mA ~ mH

,WW.. couplsuppressed

with CEDP:•h,H may beclearly distinguishableoutside130+-5 GeV

range, •h,H widths are quite different

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With CEDP the mass range up to 160-170 GeV can be covered at medium tan and up to 250 GeV for very high tan , with 300 fb-1

Helping to cover the LHC gap?

Needs ,however, still full simulation pile-up ?

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● Hbb in the high mass range (MA180-250 GeV)

-unique signature for the MSSM, cross-sections overshoot the SM case by orders of magnitude.-possibility to measure the Hbb Yukawa coupling,-nicely complements the conventional Higgs searches - CP properties, separation of H from A, -unique mass resolution,-may open a possibility to probe the ‘wedge region’ !?-further improvements needed ( going to high lumi ?....) (more detailed theoretical studies required )

● h, Hbb, in the low mass range (MA < 180 GeV)

-coverage mainly in the large tan and low MA region, -further improvements (trigger efficiency….) needed in order to increase coverage

-

Ongoing studies (together with S. Heinemeyer, M.Ryskin, W..J. Stirling, M.Tasevsky and G. Weiglein)

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mhmax scenario, =200 GeV, MSUSY =1000 GeVhbbPRELIMINARY

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Hbb PRELIMINARY

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● h,H in the low mass range (MA<180 GeV)-essentially bkgd –free production,-need further improvements, better understanding.., -possibility to combine with the bb-signal(trigger cocktail …)

-can we trigger on without the RP condition ?

● h WW -significant (~4) enhancement as compared to the SM casein some favourable regions of the MSSM parameter space.

● small and controllable backgrounds

● Hunting the CP-odd boson, A

a way out : to allow incoming protons to dissociate (E-flow ET>10-20 GeV) KKMR-04

pp p + X +A +Y +p

At the moment the situation looks borderline

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small eff scenario

for the SM Higgs at M = 120 GeV = 0.4 fb, at M= 140 GeV = 1 fb

mh 121-123 GeV

hWW PRELIMINARY

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Current understanding of the bb backgrounds for CED production

for reference purposes SM (120 GeV)Higgs in terms of S/B ratio (various uncrt. cancel) First detailed studies by De Roeck et al. (DKMRO-2002)

Preliminary results and guesstimates – work still in progress

S/B1 at ΔM 4 GeV

Four main sources (~1/4 each)

gluon-b misidentification (assumed 1% probability) Prospects to improve in the CEDP environment ? Better for larger M.

NLO 3-jet contribution Correlations, optimization -to be studied.

admixture of |Jz|=2 contribution

b-quark mass effects in dijet events Further studies of the higher-order QCD in progress

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The complete background calculations are still in progress (unusually large high-order QCD and b-quark mass effects).

Optimization, MC simulation- still to be done

Mass dependence of the SM(CEDP): SH~1/M³ Bkgd :ΔM/M for ,

ΔM/M for

( ΔM ,triggering, tagging etc improving with rising M)

6

8

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MS MSSMPRELIMINARY

V.A.Khoze, S.Heinemeyer, W.J.Stirling, M.Ryskin ,M. Tesevsky and G. Weiglein in progress

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MS MSSM PRELIMINARY

V.A.Khoze, S.Heinemeyer, W.J.Stirling, M.Ryskin, ,M. Tesevsky and G. Weiglein in progress

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MSSM

V.A.Khoze, S.Heinemeyer, W.J.Stirling, M.Ryskin M. Tesevsky and G. Weiglein in progress

PRELIMINARY

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Spin Parity Analysis

• Azimuthal angle between the leaprotons depends on spin of H

• Measure the azimuthal angle of the proton on the proton taggers

Azimuthal angle between the leading protons depends on spin of H

angle between protons angle between protons with

rescattering effects included

KKMR -03

0

0

-

+

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CP evenCP odd active at non-zero t

Azimuthal asymmetry in tagged protons provides direct evidence for CP violation in Higgs sector

Probing CP violation in the Higgs Sector

‘CPX’ scenario ( in fb)

KMR-04

A is practically uPDF - independent

Results in tri-mixing scenaio (J.Ellis et al) are encouraging, (KMR in progress)

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Hunting the CP-odd boson, A

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Hunting the CP-odd boson, A

(LO) selection rule – an attractive feature of the CEDP processes, but……

the flip side to this coin: strong ( factor of ~ 10² )suppression of the CED production of the A boson.

A way out : to allow incoming protons to dissociate (E-flow ET>10-20 GeV) KKMR-04

pp p + X +H/A +Y +p (CDD)

in LO azim. angular dependence: cos² (H), sin² (A), bkgd- flat

challenges: bb mode – bkgd conditions -mode- small (QED)bkgd, but low Br

A testing ground for CP-violation studies in the CDD processes (KMR-04)

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within the (MS) MSSM, e.g. mh scenarios with =±200 (500) GeV, tan=30-50

CDD(A->bb) ~ 1-3 fb, CDD(A->) ~ 0.1-03 fb CDD(H)~-CDD(A)

max

bb mode –challenging bkgd conditions (S/B ~1/50).

-mode- small (QED) bkgd, but low Br

situation looks borderline at best

‘best case’ (extreme) scenario

mh with =-700 GeV , tan =50, mg =10³GeV

max

CDD results at (RG) >3, ET>20 GeV

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A

in this extreme case : (Agg) Br(Abb) 22-24 MeV at MA=160-200 GeV ,tan 50,

CDD (A bb) is decreasing from 65fb to 25fb (no angular

cuts)

CDD (A) 0.8-0.3 fb

S/B ~ (A->gg) Br (A->bb) / MCD

5.5 /MCD (GeV)

currently MCD ~ 20-30 GeV…(12GeV at 120 GeV)

Prospects of A- searches strongly depend, in particular, on the possible progress with improving MCD in the Rap. Gap environment

There is no easy solution here, we must work hard in order to find way out .

We have to watch closely the Tevatron exclusion zones

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Proton Dissociative Production (experimental issues)

thanks to Monika, Michele & Albert

Measurement of the proton diss. system with ET of 20 GeV and 3<<5 -probably OK for studying the azimuthal distributions (HF or FCAL calorimeters)

Trigger is no problem if there is no pile up (Rap Gaps at Level 1); 4jet at 2*10³³ lumi- borderline

Maybe we can think about adding RPs into the trigger ( no studies so far) Maybe neutrons triggered with the ZDC (Michele )?

Can we discriminate between the cos² and sin² experimentally ?

From both the theoretical and experimental perspectives

the situation with searches for the A in diffractive processes looks

at best borderline, but the full simulation should be performed before arriving at a definite conclusion.

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…the LHC as a ‘gluino factory’ , N. Arkani-Hamed ( Pheno-05)

BFK-92

KMR-02

pp pp + ‘nothing’

further progress depends on the survival ….

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an ‘Invisible ‘ Higgs KMR-04

several extensions of the SM: a fourth generation some SUSY scenarios, large extra dimensions (one of the ‘LHC headaches’ )

the advantages of the CEDP – a sharp peak in the MM spectrum, mass determination, quantum numbers

strong requirements :

• triggering directly on L1 on the proton taggers

•low luminosity : L= 10 ³² -10 ³³ cm -2 sec-1 (pile-up problem) ,

• forward calorimeters (…ZDC) (QED radiation , soft DDD),

• veto from the T1, T2- type detectors (background reduction, improving the trigger budget)

various potential problems of the FPT approach reveal themselves

however there is a (good) chance to observe such an invisible object,which, otherwise, may have to await a ILC

searches for extra dimension – diphoton production (KMR-02)

H

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EXPERIMENTAL CHECKS

Up to now the diffractive production data are consistent with K(KMR)S results Still more work to be done to constrain the uncertainties

•Very low rate of CED high-Et dijets, observed yield of Central Inelastic dijets. (CDF: Run I, Run II) data up to (Et)min>50 GeV

• ‘Factorization breaking’ between the effective diffractive structure functions measured at the Tevatron and HERA.

(KKMR-01 ,a quantitative description of the results, both in normalization and the shape of the distribution)

•The ratio of high Et dijets in production with one and two rapidity gaps

• Preliminary CDF results on exclusive charmonium CEDP. Higher statistics is underway.

•Energy dependence of the RG survival (D0, CDF)

• CDP of γγ

(in line with the KMRS calculations)

BREAKING NEWS, CDF

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“standard candles”

First experimental results are encouraging, new data are underway

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Tevatron vs HERA:Factorization Breakdown

dN/dgap dN/dgap

p

ppIP

CDF

H1

p

ppIP

e*

tp

IPp

well

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50

51KMR expectations

CDF exclusive di-jet limits

H-mass range

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DIS04

KMR-01,70 pb47 pb

CHIC

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pp p + γγ + pKMRS-04

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BREAKING NEWS

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(KMR/ExHume)

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of Forward Proton Tagging

1. Thou shalt not worship any other god but the First Principles,and even if thou likest it not, go by thy Book.

2. Thou slalt not make unto thee any graven image,thou shalt not bow down thyself to them .

3.Thou shalt treat the existing diffractive experimental data in ways that show great consideration and respect.

4. Thou shalt draw thy daily guidance from the standardcandle processes for testing thy theoretical models.

5. Thou shalt remember the speed of light to keep it holy. (trigger latency)

6.Thou shalt not dishonour backgrounds and shalt study them with great care.

QCD

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9. Thou shalt not annoy machine people.

10. Thou shalt not delay, the LHC start-up is approaching

7.Thou shalt not forget about the pile-up (an invention of Satan).

8. Though shalt not exceed the trigger thresholds andthe L1 saturation limit. Otherwise thy god shall surely punish thee for thy arrogance.

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CONCLUSION

Forward Proton Tagging would significantly extend the physics reach of the ATLAS and CMS detectors by giving access to a wide

range of exciting new physics channels. FPT has the potential to make measurements which are unique at

LHC and challenging even at a ILC.

For certain BSM scenarios the FPT may be the Higgs discovery channel within the first three years of low luminosity running

FPT offers a sensitive probe of the CP structure of the Higgs sector.

Nothing would happen before the experimentalists & engineers come FORWARD and do the REAL WORK .

The R&D studies must be completed within 12 months (only limited time-scale and manpower available)

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From the LHCC minutes (November 2005)

The LHCC heard a report from the FP420 referee. In its Letter of Intent,the FP420 Collaboration puts forward an R&D proposal to investigate the feasibility of installing proton tagging detectors in the 420 m. region at the LHC. By tagging both outgoing protons at 420 m. a varied QCD,electroweak, Higgs and Beyond the Standard Model physics programme becomes accessible. A prerequisite for the FP420 project is to assess the feasibility of replacing the 420 m. interconnection cryostat to facilitate access to the beam pipes and therefore allow proton tagging detectors to be installed. The LHCC acknowledges the scientific merit of the FP420 physics program and theinterest in its exploring its feasibility.

LOI-submitted to the LHCC: CERN-LHCC-2005-025 LHCC-I-015

FP420 : An R&D Proposal to Investigate the Feasibility of Installing Proton Tagging Detectors in the 420m Region at LHC.

FP420 (58 physicists from 29 institutes in 11 countries)

Sub-detectors of either or both of ATLAS & CMS (common R&D route).

First opportunity –autumn 2008 (planned LHC shutdown)

FP420 detector will replace the 420m interconnection cryostat

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FP-420

The LHC start-up is approaching