higgs boson production at lhc as a probe of littlest higgs models with t-parity lei wang itp lw, j....
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Higgs boson production at LHC as a probe of littlest Higgs models with T-parity
Lei Wang
ITP
LW, J. M. Yang, PRD77, 015020 (2008)
Outline Motivation Littlest Higgs models with T-parity Single Higgs boson production via gluon-gluon
fusion Higgs-pair production via gluon-gluon fusion A Higgs boson in association with a pair of top
quarks at LHC Conclusions
Assume SM valid up to some momentum scale . Then the largest
radiative corrections to the Higgs mass are from the top quark loop:
Motivation
Maximum scale for new physics if we allow 10% fine tuning:
Ann. Rev. Nucl. Part. Sci.55, 229-270 (2005),M. Schmaltz, D. Tucker-Smith
The TeV-scale quark greatly affects the Higgs boson production processes which are dominated by top quark:
Single Higgs boson production via gluon-gluon fusion
Higgs-pair production via gluon-gluon fusion
A Higgs boson in association with a pair of top quarks at LHC
Even these Higgs boson production processes can be as a probe of different little Higgs models.
Existence of new TeV-scale quark with specific couplings to the Higgs so that the loops involving the TeV-scale quark cancel the quadratic divergence from the top quark loop .
A characteristic feature of little Higgs models:
PRD69, 075002 (2004), M. Perelstein, M. E. PeskinJHEP 0601,099, (2006), T. Han, H. E. Logan, L. T. Wang
Higgs boson is a pseudo-Goldstone boson
Combination of both couplings break global symmetry protecting Higgs mass from radiative corrections.
No 1-loop quadratic divergence!
Little Higgs mechanism(collective symmetry breaking)
Littlest Higgs models with T-parity
Littlest Higgs model
Based on non-linear sigma model.
Global symmetry:
Gauge symmetries:
(5) (5)SU SO
1 2(2) (1) (2) (1) (2) (1) (1)EMSU U SU U SU U U
Higgs is an exact Goldstone boson under either SU(3) global symmetry. Combination of both couplings breaks global symmetry enough to allow Higgs to become a pseudo-Goldstone boson.
(5) / (5)SU SO
JHEP 0207, 034 (2002), N. Arkani-Hamed, A. G. Cohen, E. Katz, A.E. Nelson
The characteristic difference between littlest Higgs models with T-parity
We comparatively study two different littlest Higgs models with T-parity. The characteristic difference is the new heavy T-quark, which cancels the quadratic divergence from the top quark loop.
Model-I: T-quark is T-even under T-parity
Model-II: T-quark is T-odd under T-parity PRD74, 055001 (2006), H. C. Cheng, I. Low, L. T. Wang
JHEP 0309, 051, 2003, H. C. Cheng, I. Low
Top-quark Yukawa interaction
1(3)SU T-parity
T-parity
Under T-parity:
Model-IJHEP 0309, 051 (2003), H. C. Cheng, I. LowPRD71, 035016 (2005), J. Hubisz, P. Meade
where i, j, k summed over 1, 2, 3 whereas x, y summed over 4, 5.
2(3)SU
Higgs interaction and mass term for top quark and partners:
The t and T are the linear combination of and .u U
where ‘+’ represents T-even and ‘-’ represents T-odd.
PRD69, 075002 (2004), M. Perelstein, M. E. PeskinJHEP 0601,099, (2006), T. Han, H. E. Logan, L. T. Wang
For , the 1-loop quadratic divergences can be canceled.
where .
Model-II
where i, j, k summed over 1, 2, 3 whereas x, y summed over 4, 5.
where l, m, n summed over 3, 4, 5 whereas r, s summed over 1, 2.
PRD74, 055001 (2006), H. C. Cheng, I. Low, L. T. Wang
Top-quark Yukawa interaction
The will introduce mixing between the light T-even and the heavy T-even fermions, which can be removed by the additional interactions,
T-parity
T-parity
Under T-parity:
1(3)SU 2(3)SU
The t and are the linear combination of and .u U T
For , Higgs interaction and mass term for top quark and partners:
The relation provides an important test of the little Higgs mechanism.
Higgs interaction and mass term for the other new quarks:
Model-I: three generations
Model-II:
The first two generations
The third generation
where .
Single-Higgs via gluon-gluon fusion
In the SM, top-quark loop dominates the amplitude.
In the model-I and model-II, the corrections are from the top-quark loops through modified coupling and loops of new T-even and T-odd quarks.
The results are not sensitive to the heavy quark mass. We take
in model-I and in model-II, and mh=150GeV. New particle scale f can be as low as 500GeV.
This process was studied in Model-I :
PLB640, 263 (2006), C. R. Chen, K. Tobe, C. P.Yuan.
1 2
JHEP 0601, 135 (2006), J. Hubisz, P. Meade, A. Noble, M. Perelstein
Single Higgs production via gluon-gluon fusion at LHC
The production cross section can be significantly suppressed.
Higgs-pair production via gluon-gluon fusion at LHC
In the SM, top-quark loop dominates the amplitude.
In the model-I and model-II, the corrections are from the top-quark loops through modified coupling and the tree-level coupling. The loops of new T-even and T-odd quarks also come into play.
htt hhtt
Higgs-pair production via gluon-gluon fusion at LHC
The production cross section can be significantly enhanced.
production at LHC
At tree-level, the correction is from the modified coupling.
ht t
htt
production at LHCht t
The production cross section can be significantly suppressed.
Conclusions The Higgs boson production processes which are dominated by to
p quark: 1. Single Higgs boson production via gluon-gluon fusion, 2. Higgs-pair production via gluon-gluon fusion, 3. A Higgs boson in association with a pair of top quarks at LHC.
Model-I and model-II can alter the SM cross sections sizably and their corrections also differ significantly. Therefore, the Higgs boson productions at the LHC may shed some light on these two models or even distinguish them.
Thanks !Thanks !
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