2,153 research outputs found
Probing CP-violating coupling in
We investigate the possibility of probing the CP-violating
coupling in the process at the future high
luminosity colliders. Our numerical results show that the cross
section for this process can be significantly increased for the allowed CP
phase and center of mass energy. For example the cross section is about 6
times of that in the standard model (SM) for and
(see text for definition). The simulation for the signal
process and its
backgrounds shows that the signal significance can reach more than
and for
respectively, with the integrated luminosity and
. For , the signal
significance can be greater than 5 for and 3.9 for
with the CP phase . Besides
the cross section enhancement, the CP-violating coupling will
induce the forward-backward asymmetry which is absent in the SM and is
a clear signal of new CP violation. Compared with the in the Higgs
decay , the can be greatly enhanced in
the production process. For example can reach 0.5 for and . Due to the large backgrounds, the
significance of the expected can only be observed at with
and . It is
essential to trigger the single photon in the final state to separate the
bottom jets arising from scalar or vector bosons, in order to isolate the
signal from the backgrounds more efficiently.Comment: Published version. 19 pages, 11 figures, 3 tables. Discussion on the
forward-backward asymmetry is adde
Four Jets as a Probe of O(100 GeV) Physics beyond Standard Model at Hadron Colliders
O(100 GeV) physics beyond the standard model (BSM) could be overlooked
provided that it is hidden in the untouched Higgs sector or jets. The top quark
forward-backward asymmetry measurements and di-jet bump, which is observed in
the associated production with charged lepton plus missing energy (supposed
arising from W decay), may indicate the existence of a new color-octet
axial-vector Z_C with a mass about 145 GeV. Here Z_C only decays into two jets.
In this paper we investigated the possibility to discover Z_C pair via
analyzing the four jets as the final states, which are heavily polluted by huge
QCD background. Our simulation showed that, however, both Tevatron and LHC have
the excellent chance to discover Z_C through analyzing the four jets events in
the current accumulated data.Comment: 15 pages, 11figures and 2 table
Deci-weak at Tevatron and LHC
Recently Tevatron released their measurements on invariant mass spectrum of
electron/positron, as well as the di-jet arising from WW+WZ production with one
W leptonically decay. Though the statistics is not significant, there are two
bumps around 240 GeV and 120-160 GeV respectively. We proposed that the two
bumps correspond to the extra light gauge bosons and ,
which couple with quarks with the deci-weak strength. In this brief report, we
also simulated di-jet invariant mass distribution at the current running LHC.Comment: 8 pages, 3 EPS figures, ref added, figures update
Searching for Charged Higgs Boson in Polarized Top Quark
The charged Higgs boson is quite common in many new physics models. In this
study we examine the potential of observing a heavy charged Higgs boson in its
decay mode of top-quark and bottom-quark in the Type-II
Two-Higgs-Doublet-Model. In this model, the chirality structure of the coupling
of charged Higgs boson to the top- and bottom-quark is very sensitive to the
value of . As the polarization of the top-quark can be measured
experimentally from the top-quark decay products, one could make use of the
top-quark polarization to determine the value of . We preform a
detailed analysis of measuring top-quark polarization in the production
channels and . We calculate the helicity
amplitudes of the charged Higgs boson production and decay.Our calculation
shows that the top-quark from the charged Higgs boson decay provides a good
probe for measuring , especially for the intermediate
region. On the contrary, the top-quark produced in association with the charged
Higgs boson cannot be used to measure because its polarization is
highly contaminated by the -channel kinematics.Comment: 21 pages, 12 figures, 2 table
New Color-Octet Vector Boson Revisit
Motivated by CDF recent measurements on di-jet invariant mass spectrum where
di-jet is associated production with charged leptons () and missing
energy, we re-examine the previous proposed massive color-octet
axial-vector-like boson . Our simulation showed that the di-jet bump
around 120-160 GeV can be induced by with effective coupling (q represents the quark other than top and is the
strong coupling constant). Moreover our numerical investigation indicated that
the top quark forward-backward asymmetry can be reproduced without
distorting shape of differential cross section ,
provided that the and top quark coupling is appropriately chosen (). Our results also showed that the
theoretical as functions of and can be
consistent with data within and respectively.Comment: 8 pages, 3 EPS figure
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