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在这项研究中,带电希格斯对的产生是在γγ对撞机超对称的情况下计算的。 在两参数非通用希格斯模型中探索了该通道,该模型提供了相对较轻的中性和带电希格斯玻色子。 将计算扩展到一个环路级别,并通过辐射光子校正来解决环路图中出现的发散。 带电希格斯对的生产率在sˆ = 635GeV时达到σˆUULO + NLO = 121fb。 还通过改变参数mA和tanβ来进行横截面分析。 在e + e-机器中具有光子光度的总旋绕横截面是根据质量中心能量的函数计算的,该质量中心能量高达1TeV,并且在s = 900GeV时,取决于电极的极化,它达到42fb。 初始电子和激光光子。
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Available online at www.sciencedirect.com
ScienceDirect
Nuclear Physics B 950 (2020) 114847
www.elsevier.com/locate/nuclphysb
Exploring the prominent channel: Charged Higgs pair
production in supersymmetric two-parameter
non-universal Higgs model
Nasuf Sonmez
Department of Physics, Faculty of Science, Ege University, 35040 Izmir, Turkey
Received 30
July 2019; received in revised form 28 October 2019; accepted 11 November 2019
Available
online 16 November 2019
Editor: Hong-Jian
He
Abstract
In this study, the charged Higgs pair production is calculated in the context of the supersymmetry at a
γγ-collider. The channel is explored in Two-parameter Non-Universal Higgs Model where the model pro-
vides
relatively light neutral and charged Higgs bosons. The computation is extended to one loop-level, and
the divergence arising in the loop-diagrams are cured with the radiative photon correction. The production
rate of the charged Higgs pair reaches up to ˆσ
LO+NLO
UU
= 121 fb at
√
ˆs = 635 GeV. The analysis of the
cross-section is also given varying the parameters m
A
and tan β. The total convoluted cross-section with
the photon luminosity in an e
+
e
−
machine is calculated as a function of the center-of-mass energy up to
1TeV, and it gets up to 42 fb at
√
s = 900 GeV depending on the polarization of the initial electron and
laser photon.
© 2019 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license
(http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP
3
.
1. Introduction
In particle physics, interactions between the fundamental particles are expressed by symme-
tries. The invariance of these symmetries leads to the conservation of physical quantities and
also imposes the equation of motion and the dynamics of the system. In this sense, the Stan-
dard Model (SM) is governed by local gauge symmetry, and it particularly has unitary symmetry
E-mail address: nasuf.sonmez@ege.edu.tr.
https://doi.org/10.1016/j.nuclphysb.2019.114847
0550-3213/© 2019
The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license
(http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP
3
.
2 N. Sonmez / Nuclear Physics B 950 (2020) 114847
SU(3) × SU(2) × U(1). Besides local gauge symmetries, there is another one called Super-
symmetry (Susy) [1] which proposes a relationship between two basic classes of fundamental
particles: bosons (particles with an integer-valued spin) and fermions (particles with half-integer
spin). The Higgs boson was discovered at the LHC [2–4]. Thus, the SM wa
s completed. How-
ever, it is believed that the SM is a low energy approximation of a greater theory which defines
new physics at higher scales. Susy is one candidate of these models which has attracted much
attention.
The LHC running at
√
s = 7, 8, 13 TeV energies made it possible to test many low scale
Susy predictions. Unfortunately, no new particle has been discovered at the LHC. That re-
stricted the Susy parameter space [5–9]; therefore, the masses of the sparticles were pushed
to higher scales. It was concluded that the simple weak scale Susy picture wa
s not valid, and
thus, new scenarios were proposed in the Susy context. The Minimal Supersymmetric Standard
Model (MSSM) [10,11]is an extension of the SM that realizes supersymmetry with a minimum
number of new particles and new interactions. The simplified versions of the MSSM can be de-
ri
ved from a grand unified theory (GUT) under various assumptions. The model was generally
defined with the following parameters: the soft-breaking masses m
0
, m
1/2
and A
0
which are
assumed universal at the GUT scale, the higgsino mixing mass parameter μ, and the ratio of
the two vacuum expectation values of the two Higgs doublets tan β. Besides these parameters,
the sparticles get a contribution from the so-called soft breaking terms. These terms miracu-
lously give extra mass to these sparticles at the weak scale so that their masses are pushed
to higher scales. These soft breaking terms are usually assumed uni
versal at the GUT scale.
It is possible to assume non-universality for some of these parameters at the GUT scale with
different motivations. For example: in one-parameter Non-Universal Higgs Model (NUHM1),
the soft-breaking contrib
utions to the electroweak Higgs multiplets (m
2
H
d
and m
2
H
u
) are equal,
m
2
H
u
= m
2
H
d
= sign(m
φ
)|m
2
φ
|, but non-universal, m
2
H
u
(GUT) = m
2
H
d
(GUT) = m
2
0
. Another one
is called the two-parameter Non-Universal Higgs Model (NUHM2) [12,13], and this time the
soft-breaking contributions to the electroweak Higgs multiplets are not equal m
2
H
u
=m
2
H
d
=m
2
0
.
This scenario fits into all the current constraints on Susy, and most importantly, all electroweak
observables get low contribution overall from radiative corrections. Thus, the NUHM2 scenario
can be adjusted easily to get outside the limits obtained by the LHC. The masses of the squarks
and the sleptons can be specially arranged a
bove the TeV scale with the lightest electroweakinos
( ˜χ
0,±
1
) and the Higgses (h
0
, H
0
, A
0
, H
±
) being set deliberately below the TeV range. Among
these particles, charged Higgs (H
±
) boson emerges naturally in extended theories with at least
two Higgs fields. The observation of a single or pair production of charged Higgs boson is a hot
research topic, and it has been studied extensively in all high-energy experiments. Its observation
will be solid proof of an extended scalar sector.
The particle physics community has several proposals for the future colliders to study the
properties of the Higgs boson and investigate the extended scalar sector. In all these proposals, a
lepton collider is planned; therefore, the next one will be an e
+
e
−
-collider. Additionally, an e
+
e
−
collider can host a γγ-collider, basically high energy electrons are converted to high energy pho-
tons with a conversion rate of k ≈ 1by Compton back-scattering [14] technique. The LHC has
not found any trace about the extra Higgs bosons or the lightest electroweakinos. Therefore, one
may wonder what is the potential of the future colliders about the supersymmetry searches, par
-
ticularly, the charged Higgs pair production. The charged Higgs pair in lepton colliders were
studied extensively before in Refs. [15,16]. Since the production rate in e
+
e
−
-collisions is s-
channel suppressed, the cross-section of γγ → H
+
H
−
is larger than that of e
+
e
−
-collider. The
production of the charged Higgs pair was investigated before at the next-to-leading order (NLO)
N. Sonmez / Nuclear Physics B 950 (2020) 114847 3
for a γγ-collider in Refs. [17,18]by taking into account only Yukawa and later full squark
correction. However, the infrared divergence was not included there. The results showed that
the one-loop corrections are from -20% to +25%. Later, the process was handled in Ref. [19]
including the real radiative corrections. The calculation wa
s presented for various benchmark
points in MSSM, and the results showed that the correction is overall between -60% to +5% at
√
s = 1TeV. From the previous works which calculated the complete one-loop corrections, it is a
proper question to ask what is the contribution of one-loop diagrams in the light of the exclusion
limits set by the LHC and whether it is possible to observe the charged Higgs bosons in future
colliders. Therefore, this process needs to be ree
valuated.
In this study, the production of charged Higgs pair is studied, including one-loop corrections
plus radiative ones. The cross-section of the charged Higgs pair is calculated as a function of
the center-of-mass (c.m.) energy. The two polarization cases, ˆσ
RR
and ˆσ
RL
, are calculated at the
NLO level. Parameters of the model are varied, and the cross-section distributions are plotted.
Additionally, the distributions are presented by convoluting the total cross-section with the pho-
ton luminosity in an e
+
e
−
-collider with various polarization configurations of the machine. The
content of this paper is organized as follows: In Sec. 2, the parameter space of the NUHM2 is de-
fined. In Sec. 3, one-loop Feynman diagrams, possible singularities in the calculation along with
the procedure to cure these divergences are discussed thoroughly. In Sec. 4, numerical results of
the total cross-section in the NUHM2 are deli
vered, and the conclusion is given in Sec. 5.
2. Two-parameters non-universal Higgs model
In Susy, the parameters at the GUT scale and the soft-breaking parameters are closely linked
with the electroweak symmetry breaking. The results from the LHC pushed the previous limits
on masses of the sparticles to high scales, and that resulted in the so-called “little hierarchy”
between the weak scale and the scale of sparticles masses. The high scale fine-tuning of the
lar
ge logarithmic contributions and the weak scale fine-tuning were needed to explain the little
hierarchy. The high scale tuning along with the weak scale tuning was discussed in detail in
Ref. [20]. The NUHM2 is an effective model which is valid up to the scale Q ≤ M
GUT
, and the
soft parameters at the GUT scale only serve to describe higher-dimensional operators of a more
fundamental theory so that there might be correlations that cancel the large logs. Then, the im-
plications on the weak scale become significant, and fine-tuning of the electroweak observables
is needed. The electroweak fine-tuning parameter
, which is defined in Ref. [21], is given below:
EW
=max
i
|C
i
|/(m
2
Z
/2) (1)
where C
H
d
= m
2
H
2
d
/(tan β
2
− 1), C
H
u
=−m
2
H
2
u
tan β
2
/(tan β
2
− 1), and C
μ
=−μ
2
. The ex-
pression of the other two contributions at the one-loop level C
u
u
(k)
and C
d
d
(k)
were defined
in Ref. [21]. Evidently, the
EW
gives the largest contribution to the mass of Z-boson. Since
NUHM2 was inspired by GUT models where
ˆ
H
u
and
ˆ
H
d
belong to different multiplets, it is
argued that the GUT scale masses m
2
H
u
and m
2
H
d
could be trade-off for the weak scale parame-
ters μ and m
A
in Ref. [22]. To achieve small
EW
, it is required that the soft mass parameter
|m
2
H
u
|, the mixing parameter of the Higgs-doublets μ, and the radiative contribution |
u
u
| have
to be around m
2
Z
/2to within a factor of a few [21,23]. Then, the |m
2
H
u
|
weak
and μ
2
can have a
value of (100 − 300 GeV)
2
at any values of the parameters m
0
and m
1/2
in the non-universal
Higgs models. Therefore m
0
= 10 TeV and m
1/2
= 0.5 TeV are assumed. The largest radiative
correction, which is stop mixing, requires A
0
=±1.6 ·m
0
=±16 TeV, and finally μ = 6TeVis
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