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Search for Strong Symmetry Breaking signals at the LHC Discovery potential

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Search for Strong Symmetry Breaking signals at the LHC Discovery potential Note: not all potential signal channels shown have been evaluated with LHC detector simulation, – PowerPoint PPT presentation

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Title: Search for Strong Symmetry Breaking signals at the LHC Discovery potential


1
Search for Strong Symmetry Breaking signals at
the LHC Discovery potential
  • Note not all potential signal channels shown
    have been evaluated with LHC detector
    simulation, but the study of these
    generic signals are certainly of high
    priority

apology bias towards ATLAS some
analysis results not yet public
2
LHC running plans
  • Present plans (still good possibility to change)
    are
  • first injections end of June
  • first physics run (typically 2 months) in 2008,
  • most likely at 10 TeV c.m. energy
  • possibly start in August or September

3
Why Dynamical Symmetry Breaking?
SM Higgs can be found at LHC with 10-20 fb-1,
and MSSM Higgss parameter space well covered
but what if not found??
Fine tuning
Unitarity
Flavour
Dark matter
while satisfying stringent constraints from
precision EW measurements
4
Variety of models of Dynamical EWSB
  • QCD-like
  • low scale technicolor
  • adjoint representations (Sannino)
  • Degenerate Bess
  • effective Chiral Lagrangian
  • extraD, higgsless
  • top see-saw
  • little Higgs
  • fourth family

5
experimental challenges backgrounds
  • Hadronic backgrounds are huge
  • ? (semi)leptonic channels only viable
  • estimates at tree level, using AlpGen (parton
    shower Matrix-element matching), with loose
    preselection Wen 2, 3, or 4 partons 500
    pb, 120 pb or 30 pb
  • large uncertainties in these cross sections
    (K-factors)
  • signals for VB scattering much weaker
  • e.g WlnZjj 2 j, (mWZ 800 GeV) 35 fb

6
Technicolor, a conservative approach
  • QCD-like, prototype theory
  • confinement of technifermions, and asymptotic
    freedom
  • chiral symmetry breaking GB long.
    components of gauge bosons ? ewsb
  • technimeson resonances
  • Extended TC embed SU(3)C,SU(NTC) and flavor in
    higher symmetry
  • to generate masses of fermions
  • but FCNCs ? ETC scale very high ( 103
    TeV) ? fermion masses too low
  • walking couplings (conformal)
  • can be achieved by large Nf, or otherwise,
    respecting asymptotic freedom and chiral SB
  • allows realistic fermion and technipion masses
  • TC scale relatively low
  • top color
  • to account (partly) for very large mass of 3rd
    family

7
EW constraints
PDG 2002
LEPSLC, 1998
(LEWWG 2005)
? minimal technicolor ruled out
8
Low Scale Technicolor
  • walking
  • large number of technifermion doublets ND ?
    relatively low scale
  • or multiscale
  • phenomenology dictated by lower scale
    Technicolor Strawman Model
  • mixing between VL and pT
  • narrow resonances
  • contribute to unitarizing GB scattering at high
    energy
  • contribute to S parameter

K.D. Lane et al, PL B388 (1996) 803
PL B405 (1997) 305
K.D. Lane et al., PR D60 (1999) 075007
PR D67 (2003) 115011
9
Strawman Model
  • present limits
  • implemented in PYTHIA
  • small S ?

S. Mrenna
(J. Hirn, V. Sanz, hep-ph/0612239, disputed R.
Foadi et al., arXiv0712.1948)
10

clean signal, but low BR
GA, K. Black, T. Bose, J. Ferland, Y. Gershtein,
K. Lane and A. Martin, Les Houches report,
arXiv0802.3715
PGS simulation
11

BRs vary strongly if
CMS
CMS TDR, p. 497, Note 2006/135
12

signif 10 s
GA, K. Black, T. Bose, J. Ferland, Y. Gershtein,
K. Lane and A. Martin, Les Houches report,
arXiv0802.3715
13

signif 8 s
GA et al, Les Houches report, arXiv0802.3715
14
  • discovering a technipion ? clear indication
    of technicolor nature of new physics
  • pT decays principally to heaviest fermion pair
    possible
  • but top coupling suppressed (Top-color assisted
    TC)
  • high backgrounds, but good Z reconstruction and
    possibility ofseeing 3 resonances !
  • large uncertainties will need data driven
    optimization

15

GA et al, Les Houches report, arXiv0802.3715
ATL-PHYS-CONF-2008-003
16

present Tevatron limits
from PDG
  • Strawman model 5s discovery of rT/wT ? mm, of
    mass 600 GeV with 1 fb-1 at LHC
  • more difficult to determine the nature of new
    physics
  • Z (from E6, for example , or
    )?
  • G (KK state of graviton)?
  • possibly use angular, rapidity distributions,
    eventually spin correlations (in tt)

(details not yet public)
17
Tevatron searches
from PDG
18

A. Belyaev, A. Blum, R. S. Chivukula and E. H.
Simmons, Phys. Rev. D72, 055022 (2005)
- 2nd lightest pT has anomalous couplings to
gluons ? large production enhancement relative
to SM Higgs
enhancement factors for 130 GeV P relative to SM
Higgs
cross sections and 5s-discovery (30 fb-1) at the
LHC ? same search as for SM Higgs, but can be
extended to higher masses
1 one-family model2 one family model with
light d-type tc-fermions3 multiscale4
low-scale
19
Chiral Lagrangian, a bottom-up approach
  • In absence of light Higgs, ewsb realized
    non-linearly
  • low energy Fermi theory, VBs are not explicit
  • at low energies, interactions of quarks dominated
    by QED and QCD
  • dimension 3 and 4 operators of the type
  • weak interactions are present in the form of
    current-current interactions (Fermi interaction)
    of dimension 6
  • at masses mW, we introduce the W and Z vector
    fields with explicit SU(2)Lx U(1)Y symmetry

20
The Chiral Lagrangian
  • and terms violating the symmetry
  • to solve the problem, introduce a field S with
    appropriate transformations under SU(2)Lx U(1)Y
    (non-linear sigma model)
  • field S is a unitary 2 x 2 matrix (3 degrees of
    freedom)
  • fermion mass terms respect
    the symmetry
  • VB mass terms arise from k.e. terms of the S
    field
  • massive VBs defined from combination

ref W. Kilian, EW Symmetry Breaking, the
Bottom-Up approach, Springer tracts 198
21
anomalous couplings
  • Assuming CP invariance, additional dim-4
    operators are possible
  • expansion of leads to
    infinite order representing a loop expansion by a
    power series in terms of

22
VB scattering in ChL
  • Assuming custodial symmetry
  • (assume global SU(2)L x SU(2)R breaking to
    SU(2)C VBs singlet under SU(2)R )
  • only 2 terms describe VB scattering
  • One can map out the parameter space explorable by
    LHC
  • in the presence of a Higgs C Ruwiedel, M
    Schumacher, N Wermes, ATL-COM-PHYS-2006-070
  • and more generally S. Belyaev et al., Phys Rev
    D59 015022 (1998) O J P Éboli et al.,
    hep-ph/0606118

23
Unitarization
  • Unitarization of ChL
  • must assume some unitarization procedure at high
    mass since we dont have a full expansion
  • Padé (or Inverse Amplitude) Method
  • very good description of pp scattering and
    resonances
  • K-matrix non-resonant (implemented in Whizard
    MC)

Dobado et al., Phys.Rev. D62 (2000) 055011
Erkcan Ozcan, UCLondon
24
Forward Jet tagging and central jet veto
  • fwd jet tagging in VB fusion processes
  • QCD vs VV scattering
  • gg fusion contribution to (H) resonance
    production has distinctive azimuthal
    distribution
  • pileup effects
  • intense activity in the forward region at high
    luminosity can fake forward jets
  • jet veto
  • no color connection between the two VBs ?
    reduced jet activity in the central region
  • efficient at rejecting ttbar, for example

VB scattering
D. Rainwater, hep-ph/0702124
QCD background
V. Del Duca et al. / Nuclear Physics B 616 (2001)
367
QED background
25
heavy jet mass
  • Highly boosted W or Z ? jj yield single jet
  • W Z j j appears as W3j or Z3j for pT gt 250 GeV
  • can select jets with mass close to mV but would
    like to be sure that they are made up of two
    subjets
  • Ysplitter
  • use kT algorithm on jet constituents and get
    y-value at which one switches from 2 to 1 jet ?
    measure of subjet structure and mass of decaying
    boson
  • cone or kT with smaller radii
  • also provide information on subjet structure

J. M. Butterworth, B. E. Cox and J. R. Forshaw,
Phys. Rev. D 65 (2002), hep-ph/0201098
Method also suggested for search of vector
quarksW. Skiba, D. Tucker-Smith,
hep-ph/0701247B. Holdom, hep-ph/0702037
26
YSplitter
- kT jet algorithm, with R 0.5 - Cuts applied
pT(jet) gt 300 GeV,
preliminary
preliminary
Even after mass cut, y cut rejects 65 of Wjets
bg with signal efficiency of 80
27
subjets with cone algorithm
preliminary
preliminary
Other observables also considered jet
moments dipole moment
28
Search at the LHC
Sorry, preliminary results not ready to be
shown, yet.
typically a few 10s to 100 fb-1
required for discovery of resonances of
mass 500 GeV to 1 TeV eventually,
distinguish scalar from vector
resonance in WW channelnonresonant channel very
difficult
variety of channels
29
Minimal Walking TC
R. Foadi et al., arXiv0706.1696, 07121948F.
Sannino, arXiv0804.0182 and ref. thereinT.
Appelquist et al., hep-ph/9906555
  • doublet of technifermions in adjoint
    representation of SU(2)
  • Interesting features
  • nearly conformal (walking), with only 2
    techniflavours
  • satisfies ew constraints
  • dark matter candidate possible
  • new heavy lepton
  • light Higgs 150 GeV
  • possibility of unification of couplings

model is being implemented in MC generator
(CalcHep, Sherpa)
30
Other models
  • Higgsless model
  • KK states of g , WA. Birkedal et al,
    hep-ph/0412278R. Malhotra, hep-ph/0611380
  • s-channel of gives rise to resonance
  • regularization of VV crosssection by tower of
    KKstates
  • Little Higgs
  • (not strong dynamics)
  • higgs as a pseudo GB of larger global symmetry
    breaking
  • rich phenomenology heavy isosinglet u-type
    quark, W, Z, triplet Higgs

31
heavy quarks
  • isosinglet heavy top
  • in top see-saw model condensate with top to
    produce heavy Higgs 600 GeV will be
    consistent with v 250 GeV
  • also found in little Higgs models
  • isosinglet D-type quarks, in E6
  • 4th family

B. Dobrescu, C. Hill, PRL 81 (19998) 2634R.S.
Chivukula, PRD 59 (1999) 075003
3 parameters mt, mT, and Yukawa coupling ratio
l1/l2
B. Holdom, hep-ph/0702037, arXiv0705.1736
32
Conclusion
  • Dynamical SB scenarios have received less
    attention than they deserve, relative to SM or
    SUSY
  • because of S-parameter ? death of Technicolor
  • too contrived?
  • Some interesting scenarios suggested
  • ew constraints generally satisfied
  • some generic features and predictions
  • VB resonance, also in VB scattering
  • rho-like resonances, possibly wide spectrum, even
    light Higgs
  • technipions
  • extra families leptons, heavy quarks
  • With few fb-1, some simple channels, if were
    lucky, could be discovered combination of
    channels will be needed to understand the tru
    nature of new physics behing the DSB

33
backup
34
Higgs search a reminder
hep-ph/0702124
35
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36
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