High Precision Spectrometers project in CMS Krzysztof Piotrzkowski (UCLouvain/CERN) Introduction &...

High Precision Spectrometers project in CMS

Krzysztof Piotrzkowski (UCLouvain/CERN)

Introduction & Motivation HPS concept and staging

HPS240 case

Workshop on Diffractive and Electromagnetic Processes at the LHC,

4-8 January 2010, ECT*, Trento

New forward detectors:

2Trento, 6/1/2010K. Piotrzkowski

JINST 4 (2009) T10001

Brief history:

May’05: R&D proposal acknowledged by LHCC

June’08: FP420 Report

Fall’08: Proposals to CMS/ATLAS

In 2009: Adding detectors @ 220/240 m

FP420

FP420

Exclusive Higgs bosons at LHC

Main motivation for FP420

Higgs kinematics fully reconstructed with forward detectors! Access to Higgs mass and quantum numbers.

SM Higgs signal statistically limited, larger for MSSM case:

Brief history:

Białas & Peschanski ’96

Albrow & Rostovtsev ’00

Khoze et al. ’02

K. Piotrzkowski 4

HPS: Motivation

Trento, 6/1/2010

Light Higgs boson case is compelling more than ever – exclusive production provides unique information:

• Higgs quantum numbers (spin-parity filter)• Direct & precise H mass measurement (event-by-event);

MH resolution of 2 GeV direct limits on Higgs width• Possibility of detecting H bb mode

Detection of SM Higgs boson requires (very) large luminosity (sobs 0.1-0.2 fb) and challenging timing detectors to keep backgrounds low (S/B1:2); in case of BSM physics HPS could provide discovery channels for Higgs bosons

In addition, HPS offers access to ‘guaranteed’ and unique studies like electroweak physics in two-photon interactions, or new QCD phenomena in exclusive production, for example.

Trento, 6/1/2010 K. Piotrzkowski 5

Observation of Exclusive Charmonium Production andgg → μ+μ- in pp Collisions at √s = 1.96 TeV

K. Piotrzkowski 6Trento, 6/1/2010 More tomorrow…

Two-photon physicsMSSM: 100 fb-1 (no pileup)

Large rates for WW

arXiv:0908.2020

HPS240 only range

More tomorrow…

K. Piotrzkowski 6

HECTOR: JINST 2, P09005 (2007)For nominal low-b LHC optics

Optimal places for tagging Central Exclusive Production (CEP)at LHC: @ 220/240m and 420m from IP

Trento, 6/1/2010

Forward proton detectors @ 420 m


• Installation of Si detectors in cryogenic region of LHC, i.e. cryostat redesign needed• Strict space limitations rule out Roman Pot technology, use movable beampipe instead• Radiation hardness required of Si is comparable to those at SLHC, use novel 3-D Silicon technology• To control pile-up background use very fast timing detectors (s ~ 10ps)

Acceptance: (At nominal LHC β* = 0.5 m)0.002 < ξ < 0.02

Two detector stations per arm (4 in total): each station contains tracking and timing detectors

Moving Hamburg pipe concept


Successfully used at HERA:Robust and simple design, + easy access to detectors

Motorization and movement control to be cloned from LHC collimator design

Moving pipe: Detector ‘pockets’


Thin 300 mm entrance and side windows by electro-erosion

In preparation for beam tests:

Hamburg moving beam pipe prototypeUCLouvain

• Two pockets laser welded ready for test beam

Picosecond ToF detectors


At nominal luminosity event rate so high @ FP420 that accidental overlays (= interesting event in central detector + two protons from single diffraction) become major background!

Use very fast ToF detectors to reduce it by matching z-vertex from central tracking with z-by-timing from proton arrival time difference:LHC vertex spread is ~50 mm to reduce significantly backgrounds one needs ~10 ps time resolutions ( 2 mm z-vertex resolution)!

Developed very fast timing detectors: Cerenkov radiators + fastest MCP-PMTs

Very challenging environment pushing MCP-PMT performances to the limits:® High event rates, up to several MHz® Running MCP-PMTs close to maximal anode currents® Large annual total collected anode charges (~10 C/cm2!)

GasToF: Gas (C4F10) Cerenkov detector with very fast light pulse (< 1 ps!) resolution limited by TTS of MCP-PMTs and electronics

Quartic: Quartz based Cerenkov with fine segmentation – multi-hit capability

Going beyond requires new ideas: sub-picosecond streak cameras??

GasToF: Cosmic-ray tests


Resolution < 20 ps for 1 p.e.!

Proton fluence at FP420


HECTORVery high fluence due to protons in single diffraction:

Distribution of protons @ FP420 in lateral plane:

® Small area detectors needed (~several cm2)® At nominal luminosity large event rates expected ~10 MHz !!® Total fluence of protons > 1015 / cm2

Reconstruction: Chromacity grids


HECTOR

Basic principle:• Three initial variables(position+angle+energy) and two measured (position+angle) assume nominal vertex position (x=0)• (Horizontal and vertical planes independent)

In each arm (and plane) position and angle @ HPS give energy loss and scattering angle @ IP

10 mm per point and ~10 m lever arm results in about 2.10-4 energy resolution!

Calibration with exclusive di-muons


pp pp l+l-

• Nearly pure QED process• Calibration/alignment of FP420 detectors

(about 40% protons detected!):

Expected resolution of x=Eg/E is ~5.10-6 !

~ 700 events in 100 pb-1 (single-interaction data @ 14TeV)

CMS thesis: X. Rouby

Calibration procedure itself can be very well controlledusing Upsilon signal!

BOTTOMLINE: Exclusive low-mass dimuons crucial for FP420

Forward proton acceptance @ b* = 0.5 m


HECTOR: JINST 2, P09005 (2007)

To detect forward protons for CEP of light Higgs (Mh ~ 120 GeV) one needs FP420 detectors; Note: Acceptance is mostly driven by energy loss NOT scattering angle (pT)

HPS240 essential for triggering + efficiency for HPS240+HPS420 ~ 2 x HPS420 only

• Tagging at 420m and 240(220)m is complementary – together ~ 0.2-10% energy loss range is covered !

• This leads to significantly higher tagged cross sections

• Both 220 and 240 m locations are ‘warm&free’ – just bare

beam-pipes

• At IP5, locations at 220 m are occupied by TOTEM -> go 240m (as ALFA in ATLAS) - it is still possible to send triggers to CMS!

• One does not need to modify the LHC beamline -> can be done before HPS420 and be treated as a proof-of-principle project (= use FP420 detector concepts) + interesting physics with HPS240 only !!

HPS proposal: Adding HPS240 detectors

19K. PiotrzkowskiTrento, 6/1/2010

HPS acceptance with newest LHC optics b* = 0.55 m


Note: 2 and 4 mm approach assumed for HPS 240 and 420 (introduce some shadowing)

N. Schul & J. de Favereau



Realistic case: 2.5 mm approach of HPS240 and 0.5 mm dead edge (=2mm physical approach)

N. Schul & J. de FavereauUsing two-photon spectra!

Note: Acceptance for pp pXp changes when central system X is constrained - here |rapidity(X)| < 1.5

Trento, 6/1/2010 22K. Piotrzkowski

LHC beam-line close to 240 m

TOTEM

From Detlef: • Space above quench resistors (QRs) is not reserved yet• Space between QR and beam pipe ~ 25 cm, and space

between QRs ~ 50 cm• No problem of heat load

Available space of ~12 m!


Taken on 14/1/2009

~240m from IP5

Q6CMS

Quench resistors

To alcove

K. Piotrzkowski 24Trento, 6/1/2010

HPS420

~250m

K. Piotrzkowski 25

HPS: Staging

Trento, 6/1/2010

HPS requires original and challenging detector solutions – novel mechanical concept (= moving pipe 1st used at HERA) + pico-second resolution ToF detectors

HPS420 detectors are essential for Higgs detection but require significant LHC beam-line modification (2 New Connection Cryostats for Point 5) long shutdowns and significant costs

HPS240 detectors are important since can provide L1 signals and installation require minimal intervention to LHC (NB: HPS detectors are ‘like’ a couple of new collimators, among 100…)

Stage 0: Proof-of-principle experimentIn close collaboration with LHC groups develop moving pipes ready for installation @240 m; test ToF detectors + associated electronics

K. Piotrzkowski 26

HPS: Staging

Trento, 6/1/2010

Stage 0: Proof-of-principle experimentDemonstrate in-situ performance of timing detectors (resolutions, resistance to backgrounds, etc) ; learn to operate near-beam detectors; characterize backgrounds etc.

Stage 1: HPS240 for CMSAdd simple trackers based on CMS barrel pixels + L1 trigger detectors; after integration of all detectors into CMS DAQ start unique studies – search for exclusive production of SUSY pairs, stringent tests of SM gauge boson sector, for example .

Stage 2: Final HPS configurationHunt for exclusive Higgs can start using ultimate detectors – new trackers and timing detectors (Note HPS stage 2 as ‘test-bench’ for CMS phase 2 DAQ/tracker + HPS420 in L1 is possible in phase 2!)

Stage 0/1: As final stage of moving pipe R&D install (in 2011?) first station with fast timing detectors + position hodoscopes

Stage 1: After HPS approval, install two HPS240 stations (in 2012-13?) with tracking based on modified CMS pixel sensors

Note: Good resolution in energy loss expected already for rather poor detectors – eg. For 100 um spatial resolution expect about 2% energy resolution for a 300 GeV loss!

Essential exercise for the final HPS design – handling of backgrounds, operation aspects + first (tagged) physics

First bremsstrahlung measurement in pp (HPS240 +ZDC) – large cross-section – can use for fast calibration of BOTH ZDC and HPS240 (?)

NOTE: Stage 1 HPS is low cost project – can be done ‘quickly’ !

Stage 0 and 1 for HPS240

27K. PiotrzkowskiTrento, 6/1/2010


LHC Plans as announced at HCP conference, Evian, Nov 20

Summary/Outlook


• CMS HPS is (rather) small but very challenging project at the LHC

• The FP420 R&D report published, is basis of the HPS proposal

• The R&D (first) phase ends with a complete new connection cryostat design and a pre-prototyped, tested concepts for high precision near-beam detectors at LHC

• Physics case for forward proton tagging spans the central exclusiveProduction (exclusive di-jets and Higgs boson!) and gg and photon-proton physics;

If running early enough (stage 1!) give access to diffractive physics, gap survival /underlying event studies…..

• For relatively low incremental cost, forward proton detectors add significant physics potential to CMS with no effect on the operation of the LHC.

You Are Welcome to Join


Extra slides



Note: 2mm approach introduce some shadowing of HPS420

N. Schul & J. de FavereauUsing two-photon spectra!



Note: Acceptance changes when central system X is constrained - here |rapidity(X)| < 1.5

K. Piotrzkowski 34

2.5 mm approach no dead edge

Trento, 6/1/2010

SUSY case with pileup

Contribution to SUSY’09arXiv:0910.0202 [hep-ph]

(Light) SUSY case

arXiv:0806.1097 [hep-ph]

Forward detectors crucial for kinematics reconstruction (charged dilepton states only!): Unique contribution!

HPS240 accepts about 50% events !!

Supersymmetric signals at high L


N. Schul at SUSY’09: Assume 10 ps resolution on each proton

High Precision Spectrometers project in CMS Krzysztof Piotrzkowski (UCLouvain/CERN) Introduction &...

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