Post on 26-Feb-2016
description
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
Theo Geralis 88/4/2012
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??
Theo Geralis 188/4/2012
A new tracker has to be installed in the high eta region (3 – 5)
Tracker in 3<|η|<5
Theo Geralis 198/4/2012
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)
Theo Geralis 278/10/2010
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
Theo Geralis 298/4/2012
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)