Mounting evidence for a 95 GeV Higgs boson Biekötter, T.; Heinemeyer, S.; Weiglein, G.
The journal of high energy physics,
08/2022, Volume:
2022, Issue:
8
Journal Article
Peer reviewed
Open access
A
bstract
In 2018 CMS reported an excess in the light Higgs-boson search in the diphoton decay mode at about 95 GeV based on Run 1 and first year Run 2 data. The combined local significance of the ...excess was 2
.
8
σ
. The excess is compatible with the limits obtained in the ATLAS searches from the diphoton search channel. Recently, CMS reported another local excess with a significance of 3
.
1
σ
in the light Higgs-boson search in the di-tau final state, which is compatible with the interpretation of a Higgs boson with a mass of about 95 GeV. We show that the observed results can be interpreted as manifestations of a Higgs boson in the Two-Higgs Doublet Model with an additional real singlet (N2HDM). We find that the lightest Higgs boson of the N2HDM can fit both excesses simultaneously, while the second-lightest state is such that it satisfies the Higgs-boson measurements at 125 GeV, and the full Higgs-boson sector is compatible with all Higgs exclusion bounds from the searches at LEP, the Tevatron and the LHC as well as with other theoretical and experimental constraints. Finally, we demonstrate that it is furthermore possible to accommodate the excesses observed by CMS in the two search channels together with a local 2
.
3
σ
excess in the
b
b
¯
final state observed at LEP in the same mass range.
Recent results reported by the ATLAS and CMS experiments on the search for a SM-like Higgs boson both show an excess for a Higgs mass near 125 GeV, which is mainly driven by the γγ and ZZ⁎ decay ...channels, but also receives some support from channels with a lower mass resolution. We discuss the implications of this possible signal within the context of the minimal supersymmetric Standard Model (MSSM), taking into account previous limits from Higgs searches at LEP, the Tevatron and the LHC. The consequences for the remaining MSSM parameter space are investigated. Under the assumption of a Higgs signal we derive new lower bounds on the tree-level parameters of the MSSM Higgs sector. We also discuss briefly an alternative interpretation of the excess in terms of the heavy CP-even Higgs boson, a scenario which is found to be still viable.
The CDF collaboration recently reported a measurement of the
W
-boson mass
M
W
whose value shows a large upward deviation from the Standard Model (SM) prediction. The question arises whether such ...large values of
M
W
could be accommodated in extensions of the SM without violating other constraints and which phenomenological consequences this would have. A different type of deviation from the SM has been observed experimentally in the searches for light Higgs bosons. CMS has observed two excesses with a local significance of about
3
σ
in the
γ
γ
and
τ
+
τ
-
final states for a hypothetical Higgs-boson mass of approximately 95 GeV. These two excesses are compatible with the corresponding ATLAS limits. Earlier an excess was also observed in the Higgs-boson searches at LEP in the
b
b
¯
final state at the local
2
σ
confidence level at about the same mass. It was shown recently that the three excesses can be accommodated in a Two-Higgs-Doublet Model that is extended with a real singlet (N2HDM) of Yukawa type IV, while being in agreement with all other theoretical and experimental constraints. We demonstrate here that the region of the parameter space that describes the three excesses can also give rise to a large contribution to
M
W
in agreement with the recent CDF measurement. We discuss further phenomenological consequences of this scenario.
For the interpretation of the signal discovered in the Higgs searches at the LHC it will be crucial in particular to discriminate between the minimal Higgs sector realized in the standard model (SM) ...and its most commonly studied extension, the minimal supersymmetric standard model (MSSM). The measured mass value, having already reached the level of a precision observable with an experimental accuracy of about 500 MeV, plays an important role in this context. In the MSSM the mass of the light CP-even Higgs boson, Mh, can directly be predicted from the other parameters of the model. The accuracy of this prediction should at least match the one of the experimental result. The relatively high mass value of about 126 GeV has led to many investigations where the scalar top quarks are in the multi-TeV range. We improve the prediction for Mh in the MSSM by combining the existing fixed-order result, comprising the full one-loop and leading and subleading two-loop corrections, with a resummation of the leading and subleading logarithmic contributions from the scalar top sector to all orders. In this way for the first time a high-precision prediction for the mass of the light CP-even Higgs boson in the MSSM is possible all the way up to the multi-TeV region of the relevant supersymmetric particles. The results are included in the code FEYNHIGGS.
In several searches for additional Higgs bosons at the LHC, in particular in a CMS search exploring decays to pairs of top quarks,
t
t
¯
, and in an ATLAS search studying tau leptons,
τ
+
τ
-
, local ...excesses of about
3
σ
standard deviations or above have been observed at a mass scale of approximately
400
GeV
. We investigate to what extent a possible signal in these channels could be accommodated in the Next-to-Two-Higgs-Doublet Model (N2HDM) or the Next-to Minimal Supersymmetric Standard Model (NMSSM). In a second step we analyze whether such a model could be compatible with both a signal at around
400
GeV
and
96
GeV
, where the latter possibility is motivated by observed excesses in searches for the
b
b
¯
final state at LEP and the di-photon final state at CMS. The analysis for the N2HDM reveals that the observed excesses at
400
GeV
in the
t
t
¯
and
τ
+
τ
-
channels point towards different regions of the parameter space, while one such excess and an additional Higgs boson at around
96
GeV
could simultaneously be accommodated. In the context of the NMSSM an experimental confirmation of a signal in the
t
t
¯
final state would favour the alignment-without-decoupling limit of the model, where the Higgs boson at
125
GeV
could be essentially indistinguishable from the Higgs boson of the standard model. In contrast, a signal in the
τ
+
τ
-
channel can only be accommodated outside of this limit, and parts of the investigated parameter space could be probed with Higgs signal-rate measurements at the (HL-)LHC.
The particle discovered in the Higgs boson searches at the LHC with a mass of about 125 GeV is compatible within the present uncertainties with the Higgs boson predicted in the Standard Model (SM), ...but it could also be identified with one of the neutral Higgs bosons in a variety of beyond the SM (BSM) theories with an extended Higgs sector. The possibility that an additional Higgs boson (or even more than one) could be lighter than the state that has been detected at 125 GeV occurs generically in many BSM models and has some support from slight excesses that were observed above the background expectations in Higgs searches at LEP and at the LHC. The couplings between additional Higgs fields and the electroweak gauge bosons in BSM theories could be probed by model-independent Higgs searches at lepton colliders. We present a generator-level extrapolation of the limits obtained at LEP to the case of a future
e
+
e
-
collider, both for the search where the light Higgs boson decays into a pair of bottom quarks and for the decay-mode-independent search utilising the recoil method. We find that at the ILC with a centre-of-mass energy of 250 GeV, an integrated luminosity of 500 fb
-
1
and polarised beams, the sensitivity to a light Higgs boson with reduced couplings to gauge bosons is improved by more than an order of magnitude compared to the LEP limits and goes much beyond the projected indirect sensitivity of the HL-LHC with 3000 fb
-
1
from the rate measurements of the detected state at 125 GeV.
A Higgs-like particle with a mass of about 125.5 GeV has been discovered at the LHC. Within the current experimental uncertainties, this new state is compatible with both the predictions for the ...Standard Model (SM) Higgs boson and with the Higgs sector in the Minimal Supersymmetric Standard Model (MSSM). We propose new low-energy MSSM benchmark scenarios that, over a wide parameter range, are compatible with the mass and production rates of the observed signal. These scenarios also exhibit interesting phenomenology for the MSSM Higgs sector. We propose a slightly updated version of the well-known
scenario, and a modified scenario (
), where the light
-even Higgs boson can be interpreted as the LHC signal in large parts of the
M
A
–tan
β
plane. Furthermore, we define a
light stop scenario
that leads to a suppression of the lightest
-even Higgs gluon fusion rate, and a
light stau scenario
with an enhanced decay rate of
h
→
γγ
at large tan
β
. We also suggest a
τ
-
phobic Higgs scenario
in which the lightest Higgs can have suppressed couplings to down-type fermions. We propose to supplement the specified value of the
μ
parameter in some of these scenarios with additional values of both signs. This has a significant impact on the interpretation of searches for the non-SM-like MSSM Higgs bosons. We also discuss the sensitivity of the searches to heavy Higgs decays into light charginos and neutralinos, and to decays of the form
H
→
hh
. Finally, in addition to all the other scenarios where the lightest
-even Higgs is interpreted as the LHC signal, we propose a
low
-
M
H
scenario, where instead the
heavy
-even Higgs boson corresponds to the new state around 125.5 GeV.
HiggsBounds 2.0.0 is a computer code which tests both neutral and charged Higgs sectors of arbitrary models against the current exclusion bounds from the Higgs searches at LEP and the Tevatron. As ...input, it requires a selection of model predictions, such as Higgs masses, branching ratios, effective couplings and total decay widths. HiggsBounds 2.0.0 then uses the expected and observed topological cross section limits from the Higgs searches to determine whether a given parameter scenario of a model is excluded at the 95% C.L. by those searches. Version 2.0.0 represents a significant extension of the code since its first release (1.0.0). It includes now 28/53 LEP/Tevatron Higgs search analyses, compared to the 11/22 in the first release, of which many of the ones from the Tevatron are replaced by updates. As a major extension, the code allows now the predictions for (singly) charged Higgs bosons to be confronted with LEP and Tevatron searches. Furthermore, the newly included analyses contain LEP searches for neutral Higgs bosons (H) decaying invisibly or into (non-flavour tagged) hadrons as well as decay-mode independent searches for neutral Higgs bosons, LEP searches via the production modes tau + tau - H and b b macr H , and Tevatron searches via t t macr H . Also, all Tevatron results presented at the ICHEPE1410 are included in version 2.0.0. As physics applications of HiggsBounds 2.0.0 we study the allowed Higgs mass range for model scenarios with invisible Higgs decays and we obtain exclusion results for the scalar sector of the Randall-Sundrum model using up-to-date LEP and Tevatron direct search results. Program title: HiggsBounds Catalogue identifier: AEFF_v2_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEFF_v2_0.html Program obtainable from: CPC Program Library, QueenE14s University, Belfast, N. Ireland Licensing provisions: GNU General Public Licence version 3 No. of lines in distributed program, including test data, etc.: 74 005 No. of bytes in distributed program, including test data, etc.: 1 730 996 Distribution format: tar.gz Programming language: Fortran 77, Fortran 90 (two code versions are offered). Classification: 11.1. Catalogue identifier of previous version: AEFF_v1_0 Journal reference of previous version: Comput. Phys. Comm. 181 (2010) 138 External routines: HiggsBounds requires no external routines/libraries. Some sample programs in the distribution require the programs FeynHiggs 2.7.1 or CPsuperH2.2 to be installed. Does the new version supersede the previous version?: Yes Nature of problem: Determine whether a parameter point of a given model is excluded or allowed by LEP and Tevatron neutral and charged Higgs boson search results. Solution method: The most sensitive channel from LEP and Tevatron searches is determined and subsequently applied to test this parameter point. The test requires as input, model predictions for the Higgs boson masses, branching ratios and ratios of production cross sections with respect to reference values. Reasons for new version: This version extends the functionality of the previous version. Summary of revisions: List of included Higgs searches has been expanded, e.g. inclusion of (singly) charged Higgs boson searches. The input required from the user has been extended accordingly. Restrictions: Assumes that the narrow width approximation is applicable in the model under consideration and that the model does not predict a significant change to the signature of the background processes or the kinematical distributions of the signal cross sections. Running time: About 0.01 seconds (or less) for one parameter point using one processor of an Intel Core 2 Quad Q6600 CPU at 2.40 GHz for sample model scenarios with three Higgs bosons. It depends on the complexity of the Higgs sector (e.g. the number of Higgs bosons and the number of open decay channels) and on the code version.
We use MasterCode to perform a frequentist analysis of the constraints on a phenomenological MSSM model with 11 parameters, the pMSSM11, including constraints from
∼
36
/fb of LHC data at 13 TeV and ...PICO, XENON1T and PandaX-II searches for dark matter scattering, as well as previous accelerator and astrophysical measurements, presenting fits both with and without the
(
g
-
2
)
μ
constraint. The pMSSM11 is specified by the following parameters: 3 gaugino masses
M
1
,
2
,
3
, a common mass for the first-and second-generation squarks
m
q
~
and a distinct third-generation squark mass
m
q
~
3
, a common mass for the first-and second-generation sleptons
m
ℓ
~
and a distinct third-generation slepton mass
m
τ
~
, a common trilinear mixing parameter
A
, the Higgs mixing parameter
μ
, the pseudoscalar Higgs mass
M
A
and
tan
β
. In the fit including
(
g
-
2
)
μ
, a Bino-like
χ
~
1
0
is preferred, whereas a Higgsino-like
χ
~
1
0
is mildly favoured when the
(
g
-
2
)
μ
constraint is dropped. We identify the mechanisms that operate in different regions of the pMSSM11 parameter space to bring the relic density of the lightest neutralino,
χ
~
1
0
, into the range indicated by cosmological data. In the fit including
(
g
-
2
)
μ
, coannihilations with
χ
~
2
0
and the Wino-like
χ
~
1
±
or with nearly-degenerate first- and second-generation sleptons are active, whereas coannihilations with the
χ
~
2
0
and the Higgsino-like
χ
~
1
±
or with first- and second-generation squarks may be important when the
(
g
-
2
)
μ
constraint is dropped. In the two cases, we present
χ
2
functions in two-dimensional mass planes as well as their one-dimensional profile projections and best-fit spectra. Prospects remain for discovering strongly-interacting sparticles at the LHC, in both the scenarios with and without the
(
g
-
2
)
μ
constraint, as well as for discovering electroweakly-interacting sparticles at a future linear
e
+
e
-
collider such as the ILC or CLIC.
The current status of electroweak precision observables in the Minimal Supersymmetric Standard Model (MSSM) is reviewed. We focus in particular on the
W boson mass,
M
W
, the effective leptonic weak ...mixing angle,
sin
2
θ
eff
, the anomalous magnetic moment of the muon,
(
g
-
2
)
μ
, and the lightest
CP
-even MSSM Higgs boson mass,
m
h
. We summarize the current experimental situation and the status of the theoretical evaluations. An estimate of the current theoretical uncertainties from unknown higher-order corrections and from the experimental errors of the input parameters is given. We discuss future prospects for both the experimental accuracies and the precision of the theoretical predictions. Confronting the precision data with the theory predictions within the unconstrained MSSM and within specific SUSY-breaking scenarios, we analyse how well the data are described by the theory. The mSUGRA scenario with cosmological constraints yields a very good fit to the data, showing a clear preference for a relatively light mass scale of the SUSY particles. The constraints on the parameter space from the precision data are discussed, and it is shown that the prospective accuracy at the next generation of colliders will enhance the sensitivity of the precision tests very significantly.
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