A high eta (3-5) Micromegas tracker, to study hard W L W L W L W L scattering with CMS

Theo Geralis 1

A high eta (3-5) Micromegas tracker, to study hard WLWLWLWL scattering with CMS

8/4/2012

Theodoros GeralisInstitute of Nuclear PhysicsNCSR Demokritos

HEP2012: Recent Developments in High Energy Physics and CosmologyIoannina, 5 – 8 April 2012, Greece

Physics Motivation High luminosity CMS upgrade A high eta tracker in CMS Micromegas technology Detector requirements Prospects

Higgs production and decays – LHC regimeMain production mechanisms

Most useful H decay modes: ZZ 4 leptons, WW lnln, gg, tt, bb?Depends on competing backgrounds and resolution we can achieve in a given channel….

dominant at LHC

second largest at LHC

Decay modes of SM Higgs

sH(120) ~ 30 pb

sH(120) ~ 5 pb

SM Higgs boson searches•SM Higgs mechanism provides one possibility to explain the EWK Symmetry Breaking. •LEP/SLD EWK data indicate a low mass Higgs with mH ~ 100 GeV

•Direct searches at LEP have given lower limits: mH > 115 GeV

•At LHC, CMS + ATLAS have narrowed the Higgs allowed space: 115 GeV < mH < 127 GeV

or mH > 600 GeV

• EWK precision measurements favor a light Higgs with SM like couplings (WW, ZZ)

EWK theory is renormalizable

Higgs allows to preserve unitarity in WW, WZ, ZZ scattering

Each one of the diagrams WWWW (below) diverges as 42 / WMs

and the sum still diverges softly as 2~)(WMsWWWWiM

Breaking of unitarity at ~ 1TeV scale

We need a scalar to restore unitarity:

Work pioneered by ..

LHC Higgs Physics scenarios (I)1) A light Higgs is discovered:

Is it a Standard Model Higgs ? Study relative Higgs Branching Ratios Is it entirely responsible for the EWK Symmetry Breaking e.g. in SUSY models the lightest Higgs h will couple with a multiplicative factor (<1):

sin(β-α).ghWW with β: tanβ=v2/v1, where v2, v1 are the two vacuum expectation values and α the mixing

angle between the two CP even neutral higgs states. In that case WWWW will become strong until it crosses

the next Higgs pole. If there are other resonant exotic particles e.g. KK excitations,

these modes will show up in the WW channel and the unitarity problem will be postponed for a scale > ~5 TeV.

We will have to study these scenarios via the vector boson scattering (WW, WZ and ZZ)

LHC Higgs Physics scenarios (II)1) A light Higgs is NOT discovered:

Scalar resonance i.e. Higgs is very heavy very broad Higgs Vector resonance, e.g. “ρTC”, V+-0

BESSWZ

New dynamical mechanism for the EWK Symmetry Breaking with strong interactions among VLVL

We will have to study these scenarios via the vector boson scattering (WW, WZ and ZZ)

Theo Geralis 78/4/2012

WWWW Cross Section calculation1) EWK Chiral Lagrangian in a series of increasing dimensions2) Build model independent higher dimensions operators3) Impose constraints in parameters from Unitarity, Causality and Precision experiments

WW generator exists: WHIZARD

Signal: usdcWW

Background: Brehmstralung

6.5 pb

0.2 pb0.002 pb

Destructive interference

σ(WW WW) = 8.5 fb !!!

(still with high uncertainties)

It can be studied in HighLuminosity LHC era :

300 – 3000 fb-1


Example:LHC discovery potential for V01

V01 is the Kaluza-Klein excitation of the Z0 boson

in Higgsless models at TeVs 14

The Vector Boson fusion/scattering at LHC

• Requires: Forward jet tagging and central jet vetoing! BUT: at HLHC/SLHC forward jet tagging and central jet vetoing suffer from big pile up, but calo method nonetheless applicable!

Forward tracking would help much!SLHC (3000 fb-1) a ~7s excess expected in W+W- scattering from

a strong coupling model (1TeV Higgs) over SM bkgd ;

jetscentralveto

W

qGeVWqP

GeVqEWWdcsupp

T

3)(

5.6)(210),(

20)(:

- scattering can be resonant or not; - if non-resonant best channel is WL

+WL+ l+n l+n but just an excess of events

- resonant models are much more appealing!Event selection

Higgs pair production and Higgs self couplingpossible justification for SLHC/HLHC…..

Higgs pair production can proceed through two Higgs bosons radiated independently (from VB, top) and from trilinear self-coupling terms proportional to HHH

SM

cross sections for Higgs boson pair production in various production mechanisms and sensitivity to HHH variations very small cross sections, hopeless at LHC

(1034), some hope at SLHCchannel investigated, 170 < mH < 200 GeV (ATLAS):

arrows correspond to variations of HHH from 1/2 to 3/2 of its SM value

triple H coupling: HHH

SM = 3mH2/v

+….

gg HH W+ W– W+ W– l±njj l±njj with same-sign dileptons - very difficult!

total cross section and HHH determined with ~ 25% statistical error for 6000 fb-1

provided detector performances are comparable to present LHC detectors

HHHSM

WZ vector resonance in VB scattering

Vector resonance (r-like) in WLZL scattering from Chiral Lagrangian model M = 1.5 TeV, leptonic final states, 300 fb-1 (LHC) vs 3000 fb-1 (SLHC)

at SLHC: S/B ~ 10at LHC: S = 6.6 events, B = 2.2 events

If no Higgs found, possibly a new strong interaction regime in VLVL scattering, this could become the central issue at the SLHC! For ex.:

Note event numbers!

These studies require both forward jet tagging and central jet vetoing! Expected (degraded) SLHC performance is included

lepton cuts: pt1 > 150 GeV, pt2 > 100 GeV, pt3 > 50 GeV; Etmiss > 75 GeV

increased cm energy/ VLHC even better!!

The CMS (Compact Muon Solenoid) detector

Simulation of a Higgs event in CMS

CMS detector design and optimisation (geometrical acceptance, energy- momentum resolution required, detector technique choices for subdetectors) have been done with the Higgs search in mind

Experimental conditions at 2x1034 cm-2 s-1 (25nsec) - SLHC/HLHC

~ 40 - 50 pile-up events per bunch crossing for operation at 2x1034cm-2s-1 and 25 nsec bunch separation - High Luminosity LHC regime (compared to ~ 300 pile-up events for the 25 nsec and ~ 400 pile-ups in 50 nsec for ultimate SLHC scenarios previously discussed for ~1035cm-2s-1) dnch/d/crossing ≈ 250 and ≈ 1250 tracks in tracker acceptance per crossing

If same granularity and integration time: tracker occupancy and radiation dose in central detectors increases by factor ~ 2, pile-up noise in calorimeters by ~ 1.4 relative to 1034

effect on: electron,g iden./purity, b-tagging performance, jets, tagging jets, e,g, isolation cuts etc.

Generated tracks, pt > 1 GeV/c cut, i.e. all soft tracks removed!

I. Osborne

H ZZ ee, mH = 300 GeV, in CMS

1035cm-2s-11032cm-2s-1

LHC operation in 2012 : pile-up L~3.3x1033cm-2s-1

Difficulties with forward tagging jets! Identify jet vertex with tracksand false jets from tracks piling in jet cone

40 reconstructed vertices!High PU run October 25, 2011Event with 20 reconstructed

Importance of VFCAL/feasibility of forward jet tagging at SLHC at ~1035 cm-2 s-1

Forward jet tagging needed to improve S/B in VB fusion/scattering processes pp qqH, qqVV …., but could also be crucial if no Higgs found by then! Or elementary H or not?

Calo method should still work at 1035: increase forward calo granularity, reduce jet reconstruction cone from 0.4 to ~ 0.2, optimise jet algorithms to minimize false jets

“tagging jet”

Forward tracking (beyond 2.4) would enormously help reducing false jets from pile-up as well as real jets from pile-up Vertices, but technique must sustain very high rates and minimize albedo to tracker

Foreseeable changes to detectors for 1035cm-2s-1 overview

changes to CMS: • Trackers, to be replaced due to increased occupancy to maintain performance, need improved radiation hardness for sensors and electronics - present Si-strip technology is OK at R > 60 cm - present pixel technology is OK for the region ~ 10 < R < 60 cm • Calorimeters: ~ OK - endcap HCAL scintillators in CMS to be changed - endcap ECAL VPT’s and electronics may not be enough radiation hard - desirable to improve granularity of very forward calorimeters - for jet tagging• Muon systems: ~ OK - acceptance reduced to || <~ 2.0 to reinforce forward shielding• Trigger(L1), to be replaced, L1(trig.elec. and processor) new ideas to include tracker in trig.

VF calorimeter for “jet tagging”Forward tracking??


A new tracker has to be installed in the high eta region (3 – 5)

Tracker in 3<|η|<5


Detector Requirements

•High Pile up vertex finding with Δz~1mm~20 – 100 μm single point precision (function of η)

•Radiation hard detector (will depend on the final detector location along z

axis)

•Affordable to build

•Long term stability

Micromegas detector is considered as a good candidateTo be confirmed by a proposed R&D

20

The Micromegas principle

Hole diameter=50μm, pitch=100μm

Spacersh=50μm

•Excellent x-y resolution•Good Energy resolution•Very low background•Excellent stability•Radiation hard•Cheap•Variety of applications (X-rays, tracking, neutron det. TPC detector, Visible photon det. )Micromegas: MICRO MEsh GAseous

Structure detector

Micromegas development - Bulk technology

pillar

pad

Well established technique

Woven Inox mesh 30 µm

vacrel 128 µm

Readout pads

Readout plane + mesh all in one

Bulk MicromegasThe pillars are attached to a woven mesh and to the readout plane

Typical mesh thickness 30 μm, gap 128 μm

Uniformity, robustness, lower capacity, easy fabrication, no support frame, small surrounding dead region: Large area detectors Curved surfaces Mass production!

Microbulk Micromegas detector

Microbulk TechnologyThe pillars are constructed by chemical processing of a kapton foil, on which the mesh and to the readout plane are attached. Mesh is a mask for the pillars!

Good properties: uniformity, clean materials, stability, good Energy resolution (<13% FWHM @ 6 keV), low mass detector, very flexible structure. IMPRESSIVE: low background Improvement from ~10-4 ~10-7 cts/keV/cm2/s

BUT: It is fragile and the mesh can not be replacedComplex procedure to produce it, particularly in conjunction with the x-y readout

Readout plane + mesh all in oneMicromesh5µm copper

Kapton 50 µm

Readout pads

Fake 2DIt works thanksto charges diffusion

I. Giomataris

The ATLAS muon project MAMMA:a successful sLHC detector case

talk by G. Tsipolitis

P. Colas et al., NIMA535(2004)506

ATLAS resistive planesMAMA project

Micromegas on a resistive thin ceramic substrateReadout pixels or strips is an independent element

Signal propagates through capacitive coupling without loss (~ 90% pass through)Ceramic provide large dynamic range of dielectric constants

In a first prototype: 300 m thick alumina+ruthenium oxide 10 m layerThis was the anode plane of a standard Bulk Micromegas

25

CAST MicroMegas in operation

CAST MicroMegas Assembly phase at INP

Micromegas activities at INP (since 2001): Built the first 4 Micromegas detectors, used in CAST, in collaboration with Saclay and CERN

27/3/2010 26Theo Geralis

Micromegas activities at INP : Prototype mM TPC: INP Design/Construction Application: Fission studies

Aluminum Housing Plexiglas Cage32 x 1ΜΩ

E field shaper

Cf source

Energy spectrum

Nuclei Energy spectrum: Sum of Strips’ Energy

252Cf nA1 + 252 – n – (4)A2 + (n,α)


Development of Radiation hard muon detectors for super LHC(operate at ~106 neutrons.cm-2s-1. Tests performed also in the Tandem accelerator)RD51 telescope: Collaborative effort INP/NTUA

RD51 Telescope (tracker):

3 x-y Micromegas detectorsIn the H6 SPS beam. The detectorsWere machined and built at INP Data Acquisition system. It was developed at INP

Telescope in RD51Test beam

TelescopeCosmics setup

Micromegas activities at INP :Micromegas for sLHC- Collaboration INP, NTUA

Later development: MAMMAAchieved space precision:

~45 μm, with 500 μm pitch can do ~25 μm, with 250 μm pitch

See talks by T. Alexopoulosand G. Tsipolitis

Summary of physics possibilities at the SLHC - phases I and II

- EW physics: refine TGC limits, start looking for QGC ie WWW, WWZ final states with all W ln, Z ll - extend search/exclusion of FCNC top decay modes t Zc, gc….

- extend (phase I) the discovery domain for massive MSSM Higgs bosons A, H, H±

in t and decay modes, as t and efficiencies should be little degraded by a factor of ~ 2 in pileup rate relative to nominal

- In the Higgs sector (phase II):precision measurements would allow to clarify the structure of the Higgs sector of the theory, ie more doublets, or singlets, whether Higgs is fundamental or composite, the nature of fermion masses (Higgs couplings to matter) What is needed:- WW, ZZ, WZ scattering at large invariant masses,- double-Higgs production,- Higgs decay branching ration measurements at the 10% level or better- study new rare H decay modes (H , H g,

- extend search/exclusion of new gauge bosons, KK excitations- extend or complement - or exclude further - SUSY spectrum


Conclusions•Irrespectively whether a Higgs is discovered or not Vector Boson scattering (WW, WZ, ZZ) offers a great tool for studying the nature of the EWSB and possibly physics BSM. •This is a high luminosity study since the cross sections are low and is planned for the sLHC/HLHC era.

•The LHC experiments have to strengthen 1) their forward jet tagging with a refined resolution, 2) their forward tracking capability at high eta to resolve vertex ambiguities from the high pile up

•Micromegas is already among the detectors to be used for the ATLAS muon system at high eta.

•We propose an R&D within CMS to study the Micromegas technology as a possibility for tracking at high eta (3-5)

A high eta (3-5) Micromegas tracker, to study hard W L W L W L W L scattering with CMS

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