M. Albrow CT-PPS DIS 2015 1

The CMS-TOTEM Precision Proton Spectrometer CT-PPS

Michael Albrow (Fermi National Accelerator Laboratory, USA) DIS 2015 April 2015

On behalf of the CMS and TOTEM Collaborations

M. Albrow CT-PPS DIS 2015 2

Introduction: What and Who

New Roman pots

Acceptance

Physics: Electroweak (W+W-) and QCD (Jets and not jets)

Tracking

Timing

Plan, schedule

Summary

p + p p + X + p

M. Albrow CT-PPS DIS 2015 3

Project to add to CMS precision tracking and timing detectors at z = ± 204 – 215 mwith TOTEM in new Roman pots, capable of operating at high luminosity(normal running) to study p + p p + X + p events. Collaboration of CMS and TOTEM.

CT-PPS project is approved by both CMS and TOTEM managementsand by the LHCC and Research Board.

2015 : Construction, and beam tests: Roman pot operation at high luminosity.January 2016 : Installation of detectors at 204-215m in both directions2016 : commissioning and first physics data

2016-2017: Physics : M(X) > ~ 300 GeV … WW, Jets etc.

INTRODUCTION

M. Albrow CT-PPS DIS 2015

“Exclusive” reactions have the form: p + p p + X + p

where X is a fully measured state in the central region, the p are leading (xF > ~ 0.9)and no other particles are produced (rapidity gaps Δy exceeding about 4 units)

Xi

jp

p The 4-momentum transfer in the t-channel is small,typically < about 1 GeV2, so θ(p) ≈ 1/7000 & p’s go down pipe.With this kinematics only γ and IP exchanges are allowed:i + j = γ + γ, γ + P or P + Pwhere P = pomeron is a strongly interacting color singlet,at leading order a pair of gluons [gg]. QCD, needs study!

CT-PPS as addition to CMS

4

Allows the LHC to be used as a “tagged” photon-photon collider √s(γγ) >> LEP ... and as a “tagged” gluon-gluon collider (with spectator gluon)

...enabling an extension of the CMS and TOTEM physics programs into a new regime ..... both QCD and EWK physics

M. Albrow CT-PPS DIS 2015 5

Technical Design Report (TDR) CERN-LHCC-2014-021CMS-TDR-013TOTEM-TDR-003

8 September 2014

Followed by LHCC andResearch Board approval

M. Albrow CT-PPS DIS 2015 6

PROTONS

Beam line region

CT-PPStiming

TOTEMtracking

CT-PPStracking 2

CT-PPStracking 1

CT-PPS Components for 2016 running

IP5►

M. Albrow CT-PPS DIS 2015 8

Roman pots(named for CERN-Rome expt. at ISR (1971))

Previous TOTEM Roman pots couldnot be used with high beam currents:Impedance mismatch affects beams.

New cylindrical design amelioratesthat. Should operate with normal high-Loperation … as planned for CT-PPS

New pots (in horizontal plane) are installed.Insertion tests to do this year.How close can we go (3mm?)Effect on stable beam, backgrounds generated,heat generated …

Cherenkov bars (timing) shown in blue

M. Albrow CT-PPS DIS 2015 9

Transverse view (“proton’s view”)t ~ - pT

2 and ξ = 1 – pz/pbeam

γ-emission, small-tp has y ~ 0

Front tracking Back timing

Timing detector design 15mm x 12mmCircle is ξ = 0.1, t = - 2 GeV2

Where are wanted protons in the detectors at 204 m, 215 m ?

β* = 0.55 m

M. Albrow CT-PPS DIS 2015 10

Hit distribution on 204m detectorexpected for X = W+W-

Distributions in ξ, t for exclusive dijetevents accepted by CT-PPS at 15σ from beam

Normalized to 1.0 at maximum

ξ = Fractional momentum loss

|t|

≅ p T2

Acceptances

M. Albrow CT-PPS DIS 2015

Mass acceptance for two arm events

Good forW+W- and Jet + Jet (+ Jet) andBSMH(400-800)

Closer to beams gains low massacceptance

11

Acceptance is very similar for W+W- (Smaller |t| because γγ)

M. Albrow CT-PPS DIS 2015 12

PHYSICS

M. Albrow CT-PPS DIS 2015

PHYSICS:Both protons measured, M(min) ~ 300 GeV:

Exclusive dijets, M(JJ) to ~ 800 GeV. Pure gluon-jets, small ( ≈ 1 %) component ofb-bbar dijets (need double tag). Test of Jz = 0 rule. q-qbar dijets forbiddenfor massless quarks at t = 0.Test of pQCD mechanisms of exclusive production, “superhard” pomeron. Optimizing b-tagging … one b-jet means other jet is b-bar jet. Measure exclusive bJ-bJ spectrum (important for later – H?) [b-jet and homage to Bjorken!]

Measure γγ W+W-. Anomalies in WW final state interactions (but transverse,so H should not appear in γγ channel). Triple, quartic gauge boson couplings:Most sensitive searches ( >> LEP)

New resonances not completely excluded in M ~ 250 – 600 GeV.

Heavy states with “vacuum” Q.Nos & J = 0,2coupling (even indirectly like H) to gg.

QCD

EWK

& a new window for potential surprises13

IMPORTANT!

M. Albrow CT-PPS DIS 2015 14

The power of “missing mass” in exclusive processes ( = 4-momentum conservation)

Example: p + p p + W+W + p

p p

μν

JetJet

MM(pp – ppJJμ) = M(ν) = 0 ; 4-momentum of ν known.

MM(pp – ppJJ) = M(μν) = M(W) even without μ measurement.MM(pp-pp) = M(WW) ... or M(ZZ).

If exclusive ZZ JJνν, M(pp-ppJJ) = M(νν) = M(Z). Not a SM process (except for M(H*)>300 GeV)

It is only with exclusive processes* with both protons measured that these4-momentum constraints can be used. Transverse momentum px,py is in everyday use ... Missing ET (MET)

*Including elastic scattering of course, the grandmother of exclusive processes

Nomenclature: p = 4-vector of p etc

M. Albrow CT-PPS DIS 2015

At LEP: e+e- Z 2 jets (q-qbar) or 3 jets (q-qbar-g)

At LHC: IP + IP 2 jets (g-g) or 3 jets (q-qbar-g) OR (g-g-g)

Different kinematics g

g

gg

q

q

Democratic so 1/5 each quark type:20% b-bbar 20% c-cbar, ...

99% of exclusive dijets are (?) g-g (unique) 1% are b-bbar uu, dd, ss, cc suppressed by ~[m(q)/m(JJ)]2 (Durham theory gp)

p + p p + X + pM(X) > 300 GeV

Exclusive Jet Production

Gluon Jet Factory : almost no quark jet contamination

Subtle QCD effects:No gluon radiation (Sudakov)No other parton collisionsTest spin rule Jz = 0Interplay of pQCD and npQCDDistant relation to elastic scattering

CDF and D0 Observed X = JJ at √s = 1.96 TeV to ET > 30 GeV

15

M. Albrow CT-PPS DIS 2015 16

Selecting exclusive dijetsSimulations with POMWIG and PYTHIA (no exclusive JJ) and ExHuME (has exclusive JJ)Plots normalised to equal area (shape comparison)

Dijet rapidity ~ y(pp) orpz balance: pz(pp) = - pz(JJ)

Dijet mass ~ = Missing mass (pp)pT balance: pT(pp) = - pT(JJ)Full 4-momentum conservation

Harder M(JJ) spectrum--- Little additional stuff fora given ET

Exclusive trijets are alsovery interesting!

M. Albrow CT-PPS DIS 2015

From 90 m β* Run with TOTEM: p + JJ + p

REAL CMS+TOTEM EVENTS!

Cleanest dijets in a hadron collider!

17

Very clean (exclusive candidate) jet events

M. Albrow CT-PPS DIS 2015

From July 2012 90 m β* Run with TOTEM: p + JJJ + p

> = 2 jets ET > 20 GeV2 protons & FSC gaps

Exclusive 3-jet events, theory:Mostly gggSome qqg ... more open20% each bb, cc, ss, uu, ddIf one b, 2 b’s!

18

M. Albrow CT-PPS DIS 2015

But most (~ 95%?) P + P X events will not be exclusive 2- or 3-jetsFinal states in √s(PP) ~ 300 – 800 GeV is unexplored territory.

Many interesting studies.... event shapes (spherical, very high multiplicity, or ... ?) 4-jets from double parton scattering ... measures correlations between gluons in pomeronheavy flavour production, etc

Underlying event studies: now a minor industry, tuning PYTHIA to fit data

This is non-perturbative, QCD-inspired and phenomenological with tuned parameters.

Developing generators for X in p + X + p events challenges theory/phenomenologyand should lead to better understanding of strong interaction (NP-QCD) physics.

Simulations of exclusive 2-3 jets predict:In 100 fb-1 ~250 events with leading jets above ET = 150 GeV

Jets and not-Jets

19

M. Albrow CT-PPS DIS 2015

Electroweak Physics

EWK & QCD EWK - SM EWK – SM & BSMquartic gauge coupling

20

γ – Z -- IPNot with both protons detected

M. Albrow CT-PPS DIS 2015

LHC is a Photon-Photon Collider

p pγγ

Coulomb field is long rangeProtons can pass at a few fm& emerge with small pT

(intact or dissociated)

Wγγ = centre-of-mass energyof γγ collisions ...hundreds of GeV. >> LEP

UNIQUE until ILC/CLIC

21

S γγ /

GeV

Tagged photon-photon luminosity spectrumexample: 2 mm from beams at 14 TeVFrom K.Piotrzkowski, Phys.Rev D63 (2001) 071502

Double tagged

Elastic-elastic(p’s or no p’s)

All (incl. diss.)

M. Albrow CT-PPS DIS 2015

Exclusive W+W- Production

This γγWW coupling measurement is unique to PPS until TeV e+e- collidersIt was done at LEP but CT-PPS has ~ 103-4 x the sensitivity.

Standard Model γγ WW by t-channel exchange. (Not just charge Q, Yang-Mills gauge couplings)Quartic coupling, ~4 orders of magnitude beyond LEP limits. Also look for γγγγ and γγZZ (BSM)

σ (SM) = 96fb Quartic Coupling

22

M. Albrow CT-PPS DIS 2015 23

DETECTORS

24

Tracking detectors

Flex hybrid for:ReadoutPowerDSC/SS

Token Bit Manager

24 mm

16 m

m

2+2 stations6 detector planes in each station

DetectorPackagefits into existing box-shaped RPs

BeamSensors: • 16 x 24 mm2 3D silicon pixel sensors • 150(x) x 100(y) μm2 pixel pattern same as CMS pixel detectors Front-end chips:• 6 PSI46dig readout chips (52x80 pixels each)

Same readout scheme as Phase I upgrade of CMS Pixel Tracker → Existing CMS DAQ components and software can be reused

25

3D sensors by CNM

Sensors are in production at CNM (Barcelona).

CT-PPS sensors characteristics:• 2E pixel configuration, i.e. 2 readout columns per pixel• 200 μm slim edges• 2x3 sensor modules (6 PSI46dig ROCs each module)

CNM technology as for the ATLAS IBL production:

4” wafers, 230 μm thicknessDouble-sided, not passing through columns

3D sensors consist of an array of columnar electrodes • Low depletion voltage (~10 V)• Fast charge collection time• Reduced charged trapping probability and therefore high radiation hardness

M. Albrow CT-PPS DIS 2015 26

σ(t) = 30ps demonstrated (Fermilab test beam)2 modules in line 21 ps + possible improvements

TIMING is essential for PU rejection.σ(t) = 20 ps σ(z) = 4.2 mm IFF from same interaction

Test beam, 120 GeV p’s3 L-bars in lineRise time 10%-90% = 800 ps

MCP-PMT240 referencetime signal

QUARTIC: see2012 J.Inst 7 P10027

Baseline for Jan 2016:Two quartic modules in one pot.Each has 4x5 = 20 quartzCherenkov bars with SiPMs

spacers (100 μm)

M. Albrow CT-PPS DIS 2015 27

View from bottom of pot.4 x 5 array of 3mm x 3mm quartz L-bars (shown in brown)Hidden: Front end board with SiPM array

Protons direction

QUARTIC (QUARtz TIming Cherenkov) baseline for timingActive 0.4 mm from inside beam pipe.Two modules in one Roman pot.

Status : Prototype madeBeam tests early June at FermilabTwo or more in August at CERN with DAQ. Four ready for January installation in tunnel.

Double QUARTIC module inside one Roman pot

PROTONS

M. Albrow CT-PPS DIS 2015 28

GASTOF: Gas Cherenkov (~ atmospheric pressure)Very small Cherenkov angle simplifies optics (but light NPE ~ sin2θ) Detect and time single photoelectrons … 2 or 3 particles/bunch crossing?Very little optical dispersion: good timingLittle material in beam : after tracking but before QUARTIC.

MCP-PMTs had limitedphotocathodelifetimes (in # PE’s) Now resolved

Another Roman pot is reserved for additional timing systems.Better granularity (than 3mm x 3mm) is desirable near the beam pipe.

GASTOF

M. Albrow CT-PPS DIS 2015 29

TIMING ReadoutSchematic

NINO boardFast amlipfier-discriminator20 channel SiPM Mounting Front End Board

LV, Leakage current, temp and pressure monitors

M. Albrow CT-PPS DIS 2015 30

Other types of timing detector being developed:Improved granularity near beam. Solid state detectors, silicon or diamond, worse time resolution (today) butmany thin detectors can be in a stack for √N improvement … “timetrack”

Example:Low Gain Avalanche Diode (LGAD) High Voltage Ultra-Fast Silicon Detectors (UFSD)

BEAM

Not baseline, but space in potupstream of Quartics could be used

X

M. Albrow CT-PPS DIS 2015 31

Need Δt = tL – tR for z(interaction). Synchronized clocks (few ps) at L and R stations

Another system based on optical fibers is being implemented. “Belt and braces”

Reference Timing System using RF Cable

M. Albrow CT-PPS DIS 2015 32

Installation in January 2016Data taking after some weeks(months?) commissioning.Aim for 100 fb-1 before LS2

Plans and Schedule

M. Albrow CT-PPS DIS 2015

Summary

The addition of small high precision tracking and timing detectors to CMS together with the TOTEM Collaboration, CT-PPSopens up a new field of physics: p + X + p with both p’s and X all measured, at high lumi (μ ~ 30, depends on X)

QCD: Jets, gluons, interplay of pQCD and npQCD, new QCD phenomena?

EWK: Especially W+W- and BSM EWK couplings?

In addition, any special low-μ running for diffraction, e.g. low mass double pomeron exchange, can benefit from these detectors

Suitable detectors are planned for installation in new (now installed) R.pots in January

Aim for physics in 2016, run to LS2 and possibly beyond.

33

Thank you

34M. Albrow CT-PPS DIS 2015