Mass bounds on a very light neutralino

100

Electroweak baryogenesis is an attractive scenario for the generation of the baryon asymmetry of the universe as its realization depends on the presence at the weak scale of new particles which may be searched for at high energy colliders. In the MSSM it may only be realized in the presence of light stops, and with moderate or small mixing between the left-and right-handed components. Consistency with the observed Higgs mass around 125 GeV demands the heavier stop mass to be much larger than the weak scale. Moreover the lighter stop leads to an increase of the gluon-gluon fusion Higgs production cross section which seems to be in contradiction with indications from current LHC data. We show that this tension may be considerably relaxed in the presence of a light neutralino with a mass lower than about 60 GeV, satisfying all present experimental constraints. In such a case the Higgs may have a significant invisible decay width and the stop decays through a three or four body decay channel, including a bottom quark and the lightest neutralino in the final state. All these properties make this scenario testable at a high luminosity LHC.

Section: Jhep02(2013)001supporting

confidence: 88%

MSSM electroweak baryogenesis and LHC data

Carena

Nardini

Quirós

et al. 2013

100

“…[95] for this model. Some general studies regarding light neutralinos can be found in [107][108][109][110][111][112][113][114][115][116]. On the other hand, in the regime of small Yukawa coupling f ∼ 10 −4 , the Higgs boson mass is devoid of any large tree level contribution.…”

Section: Jhep02(2015)124mentioning

confidence: 99%

“…In this case, this is the lightest supersymmetric particle (LSP) and its mass is mainly controlled by the R-breaking Majorana gaugino mass parameter M 1 . A very light neutralino has profound consequences in both cosmology as well as in collider physics [107][108][109][110][111][112][113][114][115][116]. In the context of the present model one can easily satisfy the stringent constraint coming from the invisible decay width of the Z boson because the light neutralino is predominantly a bino.…”

Section: Jhep02(2015)124mentioning

confidence: 99%

“…In order to avoid the strong constraint on such a decay process coming from big-bang nucleosynthesis (BBN) one must consider an upper bound on the reheating temperature of the universe T R 10 6 GeV [111,118]. In addition, such a light state is subjected to various collider bounds [107] and bounds coming from rare meson decays such as the decays of pseudo-scalar and vector mesons into light neutralino should also be investigated [112] in this context. The spectra of low lying mass eigenstates for the large f case will be shown later for a few benchmark points.…”

Section: Jhep02(2015)124mentioning

confidence: 99%

See 1 more Smart Citation

h → γγ in U(1) R -lepton number model with a right-handed neutrino

Chakraborty

Datta

Roy

2015

We perform a detailed study of the signal rate of the lightest Higgs boson in the diphoton channel (µ γγ ), recently analyzed by both the ATLAS and CMS collaborations at the Large Hadron Collider, in the framework of U(1) R − lepton number model with a right handed neutrino superfield. The corresponding neutrino Yukawa coupling, 'f ', plays a very important role in the phenomenology of this model. A large value of f ∼ O(1) provides an additional tree level contribution to the lightest Higgs boson mass along with a very light (mass ∼ a few hundred MeV) bino like neutralino and a small tree level mass of one of the active neutrinos that is compatible with various experimental results. In the presence of this light neutralino, the total decay width of the Higgs boson and its various branching fractions are affected. When studied in conjunction with the recent LHC results, these put significant constraints on the parameter space. The signal rate µ γγ obtained in this scenario is compatible with the recent results from both the ATLAS and the CMS collaborations at 1σ level. A small value of 'f ', on the other hand, is compatible with a sterile neutrino acting as a 7 keV dark matter that can explain the observation of a mono-energetic X-ray photon line by the XMM-Newton X-ray observatory. Because of the absence of a light neutralino, the total decay width of the lightest Higgs boson in this case remains close to the SM expectation. Hence, in the small 'f ' scenario we obtain a relatively larger value of µ γγ which is closer to the central values reported recently by these two collaborations.

“…Since χ 0 1 does not decay and does not interact with the detector, no direct limit can be obtained from this process. However the precise measurement of the Z-boson width imposes a limit of m χ 0 1 45 GeV, unless the neutralino has a very small (or zero coupling) to the Z, see e.g [28]. Searches for heavier charginos and neutralinos were essentially limited by the maximal LEP II center of mass energy of 209 GeV.…”

Section: Phenomenology and Limits On Electroweakinosmentioning

confidence: 99%

Compressed electroweakino spectra at the LHC

Schwaller

Zurita

2014

138

146

In this work, we examine the sensitivity of monojet searches at the LHC to directly produced charginos and neutralinos (electroweakinos) in the limit of small mass splitting, where the traditional multilepton plus missing energy searches loose their sensitivity. We first recast the existing 8 TeV monojet search at CMS in terms of a SUSY simplified model with only light gauginos (winos and binos) or only light Higgsinos. The current searches are not sensitive to MSSM-like production cross sections, but would be sensitive to models with 2-20 times enhanced production cross section, for particle masses between 100 GeV and 250 GeV. Then we explore the sensitivity in the 14 TeV run of the LHC. Here we emphasise that in addition to the pure monojet search, soft leptons present in the samples can be used to increase the sensitivity. Exclusion of electroweakino masses up to 200 GeV is possible with 300 fb −1 at the LHC, if the systematic error can be reduced to the 1% level. Discovery is possible with 3000 fb −1 in some regions of parameter space.