Search

We briefly summarize some searches for Higgs bosons with a mass of ≲ 1 1 0  GeV at LEP and the LHC. We discuss a possible signal in the diphoton decay mode at m ϕ ∼ 9 6  GeV as reported by CMS, together with a ∼ 2 σ hint in the b b ̄ final state at LEP. We briefly review possible interpretation of such a new particle in various BSM models. We focus on possible explanations as reported within the NMSSM and the μ ν SSM. Conclusions for future collider projects are briefly outlined. [ABSTRACT FROM AUTHOR]

The higgsino world is one of the popular natural SUSY scenarios, in which $$|\mu | \ll M_{\mathrm{gauginos}} \ll M_{\mathrm{scalars}}$$ . As such, searching for light degenerate higgsinos becomes an essential task of testing naturalness in supersymmetry (SUSY). In this work, we study the indirect effects of light higgsinos in the process $$e^+e^- \rightarrow W^+W^-$$ at future Higgs factories, such as the Circular Electron Positron Collider (CEPC) in China. We find that the higgsino mass parameter $$\mu \lesssim 210 \, \hbox {GeV}$$ favored by naturalness can be covered if the accuracy of the measurement of $$W^+W^-$$ production can reach 0.1% at 240 GeV CEPC. [ABSTRACT FROM AUTHOR]

One item on the agenda of future colliders is certain to be the Higgs boson. What is it trying to tell us? The primary objective of any future collider must surely be to identify physics beyond the Standard Model, and supersymmetry is one of the most studied options. Is supersymmetry waiting for us and, if so, can LHC Run 2 find it? The big surprise from the initial 13 TeV LHC data has been the appearance of a possible signal for a new boson with a mass 750 GeV. What are the prospects for future colliders if the X(750) exists? One of the most intriguing possibilities in electroweak physics would be the discovery of nonperturbative phenomena. What are the prospects for observing sphalerons at the LHC or a future collider? [ABSTRACT FROM AUTHOR]

We present an overview on the interplay between direct searches for new physics at the LHC and indirect constraints from flavor physics, with an emphasis on the implications of the recent LHCb results. The complementarity with the Higgs search results will also be addressed. We show the correlations and complementarity between the different sectors in the context of a few specific scenarios in supersymmetry. [ABSTRACT FROM AUTHOR]

We review the No-Scale ℱ-SU(5) model with extra TeV-scale vector-like flippon multiplets and its associated collider phenomenology in the search for supersymmetry at the LHC. The model framework possesses the rather unique capacity to provide a light CP-even Higgs boson mass in the favored 124-126 GeV window while simultaneously retaining a testably light SUSY spectrum that is consistent with emerging low-statistics excesses beyond the Standard Model expectation in the ATLAS and CMS multijet data. [ABSTRACT FROM AUTHOR]

Finite Unified Theories (FUTs) are N = 1 supersymmetric Grand Unified Theories (GUTs) which can be made finite to all-loop orders, based on the principle of reduction of couplings, and therefore are provided with a large predictive power. We confront the predictions of an SU(5) FUT with the top and bottom quark masses and other low-energy experimental constraints, resulting in a relatively heavy SUSY spectrum, naturally consistent with the nonobservation of those particles at the LHC. The light Higgs boson mass is automatically predicted in the range compatible with the Higgs discovery at the LHC. Requiring a light Higgs boson mass in the precise range of Mh = 125.6 ±2.1 favors the lower part of the allowed spectrum, resulting in clear predictions for the discovery potential at current and future pp, as well as future e+e- colliders. [ABSTRACT FROM AUTHOR]

We reveal a set of novel decay topologies for the 125 GeV Higgs boson in supersymmetry which are initiated by its decay into a pair of neutralinos, and discuss their collider search strategies. This category of exotic Higgs decays is characterized by the collider signature: visible objects +ET, with ET dominantly arising from escaping dark matter particles. Their benchmark arises naturally in the Peccei-Quinn symmetry limit of the minimal supersymmetric standard model singlet extensions, which is typified by the coexistence of three light particles: singletlike scalar h1 and pseudoscalar a1, and singlinolike neutralino χ1, all with masses of ≲10 GeV, and the generic suppression of the exotic decays of the 125 GeV Higgs boson h2→h1h1, a1a1 and χ1χ1, however. As an illustration, we study the decay topology: h2→χ1χ2, where the binolike χ2 decays to h1χ1 or a1χ1, and h1/a1→ff, with f̄f=μ+μ-, b̄b. In the dimuon case (mh1/a1~1 GeV), a statistical sensitivity of S/√B>6σ can be achieved easily at the 8 TeV LHC, assuming σ(pp→Wh2)/σ(pp→WhSM)Br(h2→μ+μ-χ1χ1)=0.1. In the b√b case (mh1/a1~45  GeV), 600 fb-1 data at the 14 TeV LHC can lead to a statistical sensitivity of S/√B>5σ, assuming σ(pp→Zh2)/σ(pp→ZhSM)Br(h2→b̄bχ1χ1)=0.5. These exotic decays open a new avenue for exploring new physics couplings with the 125 GeV Higgs boson at colliders. [ABSTRACT FROM AUTHOR]

We re-investigate the scalar potential and the Higgs sector of the supersymmetric economical 3-3-1 model (SUSYE331) in the presence of the $$B/\mu $$ -type terms, which has many important consequences. First, the model contains no massless Higgs fields. Second, we prove that the soft mass parameters of the Higgses must be at the $$\hbox {SU}(3)_L$$ scale. As a result, the masses of the Higgses drift toward this scale except one light real neutral Higgs with the mass of $$m_Z|c_{2\gamma }|$$ at the tree level. We also show that there are some Higgses containing many properties of the Higgses in the minimal supersymmetric standard model (MSSM), especially in the neutral Higgs sector. One exact relation in the MSSM, $$m^2_{H^{\pm }}=m^2_{A}+m^2_W$$ , is still true in the SUSYE331. Based on this result we make some comments on the lepton flavor violating decays of these Higgses as one of signatures of new physics in the SUSYE331 model which may be detected by present colliders. [ABSTRACT FROM AUTHOR]

Abstract: We show that a muon collider is ideally suited for the study of heavy scalars, cousins of the Higgs boson found in two-Higgs-doublet models and required in supersymmetric models. The key aspects of are: (1) they are narrow, yet have a width-to-mass ratio far larger than the expected muon collider beam-energy resolution, and (2) the larger muon Yukawa allows efficient s-channel production. We study in detail a representative Natural Supersymmetry model which has a with . The large event rates at resonant peak allow the determination of the individual H and A resonance parameters (including CP) and the decays into electroweakinos provide a wealth of information unavailable to any other present or planned collider. [Copyright &y& Elsevier]

In supersymmetric models with minimal particle content and without left-right squark mixing, the conventional wisdom is that the 125.6 GeV Higgs boson mass implies top squark masses of O(10) TeV, far beyond the reach of colliders. This conclusion is subject to significant theoretical uncertainties, however, and we provide evidence that it may be far too pessimistic. We evaluate the Higgs boson mass, including the dominant three-loop terms at O(α,αs2), in currently viable models. For multi-TeV top squarks, the three-loop corrections can increase the Higgs boson mass by as much as 3 GeV and lower the required top-squark masses to 3-4 TeV, greatly improving prospects for supersymmetry discovery at the upcoming run of the LHC and its high-luminosity upgrade. [ABSTRACT FROM AUTHOR]

Abstract: We describe a model named No-Scale which is simultaneously capable of explaining the dual signals emerging at the LHC of (i) a 124–126 GeV Higgs boson mass , and (ii) tantalizing low-statistics excesses in the multi-jet data which may attributable to supersymmetry. These targets tend to be mutually exclusive in more conventional approaches. The unified mechanism responsible for both effects is the introduction of a rather unique set of vector-like multiplets at the TeV scale, dubbed flippons, which (i) can elevate by around 3–4 GeV via radiative loop corrections, and (ii) flatten the running of the strong coupling and color-charged gaugino, resulting in a prominent collider signal from production of light gluino pairs. This well-motivated theoretical framework maintains consistency with all key phenomenological constraints, and all residual parameterization freedom may in principle be fixed by a combination of the two experiments described. We project that the already collected luminosity of may be sufficient to definitively establish the status of this model, given appropriate data selection cuts. [Copyright &y& Elsevier]

I discuss LHC physics in the historical perspective of the progress in particle physics. After a recap of the Standard Model (SM) of particle physics, I discuss the high energy colliders leading up to LHC and their role in the discovery of these SM particles. Then I discuss the two main physics issues of LHC, i.e. Higgs mechanism and supersymmetry. I briefly touch upon Higgs and SUSY searches at LHC along with their cosmological implications. [ABSTRACT FROM AUTHOR]

Abstract: The Higgs sector is extended in R-symmetric supersymmetry theories by two iso-doublets which complement the standard iso-doublets . We have analyzed masses and interactions of these novel states and describe their [non-standard] decay modes and their production channels at the LHC and colliders. [Copyright &y& Elsevier]

Abstract: If the sparticles are relatively heavy (a few TeV) while the Higgs sector is not so heavy ( is not so large), the Higgs boson Yukawa couplings can harbor sizable quantum effects of sparticles and these large residual effects may play a special role in probing supersymmetry at foreseeable colliders. In this work, focusing on the supersymmetric QCD effects in the coupling (h is the lightest CP-even Higgs boson), we give a comparative study for the two popular supersymmetric models: the MSSM and NMSSM. While for both models the supersymmetric QCD can leave over large residual quantum effects in coupling, the NMSSM can allow for a much broader region of such effects. Since these residual effects can be over 20% for the coupling (and thus over 40% for the ratio ), future measurements may unravel the effects of heavy sparticles or even distinguish the two models. [Copyright &y& Elsevier]

Abstract: In models with extended Higgs sectors, Higgs-boson-mediated Lepton Flavour Violation (LFV) can naturally appear. We study the physics potential of an electron–photon collider on searching LFV processes (; ) where H and A are extra CP even and odd Higgs bosons, respectively, in the minimal supersymmetric standard model and the effective two Higgs doublet model. The production cross section can be significantly large for the maximal allowed values of the LFV coupling constants under the current experimental data. Present experimental upper bounds on the effective LFV coupling constants would be considerably improved by searching these processes, which would be better than MEG and COMET experiments and also those at LHCb and SuperKEKB. Moreover, one can separately measure chirality of effective LFV coupling constants via these processes by selecting electron polarizations. [Copyright &y& Elsevier]

The CP violating phases in soft SUSY breaking terms may induce indirect CP violation in the neutral Higgs boson sector through SUSY particle loops as well as direct CP violation in the γγ→Hi (i=1,2,3) through CP violating vertices. We present a complete analysis of the MSSM Higgs sector CP violation at photon colliders including the chargino loop contributions in the regime $\tan\beta\lesssim20$ , where the CP violating mixing in the neutral Higgs sector is very strongly influenced by the scalar top loop, more so than the chargino and neutralino ones. However, the CP violating phases of the higgsino and wino mass parameters may still generate direct CP violation in γγ→Hi. In this process, the CP violating phenomena become very rich, and thus we study the production rates and polarization asymmetries in the Higgs production in detail. Photon colliders with high luminosity and well controlled polarized initial photon beams are indispensable in determining the CP properties of neutral Higgs bosons. [ABSTRACT FROM AUTHOR]

Abstract: We propose a model that introduces a supersymmetric unparticle operator in the minimal supersymmetric Standard Model. We analyze the lowest dimension operator involving an unparticle. This operator behaves as a Standard Model gauge singlet and it introduces a new parameter into the Higgs potential which can provide an alternative way to relax the upper limit on the lightest Higgs boson mass. This operator also introduces several unparticle interactions which can induce a neutral Higgsino to decay into a spinor unparticle. It also induces violation of scale invariance around the electroweak scale. It is necessary for the scale of this violation to be larger than the lightest supersymmetric particle mass to maintain the latter as the usual weakly interacting massive particle dark matter candidate. An alternative is to have unparticle state as dark matter candidate. We also comment on some collider implications. [Copyright &y& Elsevier]

We update the upper bound on the lightest CP-even Higgs mass in the NMSSM, which is given as a function of tan β and λ. It is pointed out that large values of tan β, with λ not too small, imply a large value for the MSSM-like parameter MA. We include the available one- and two-loop corrections to the NMSSM Higgs masses, and constraints from the absence of Landau singularities below the GUT scale as well as from the stability of the NMSSM Higgs potential. For mtop varying between 171.4 and 178 GeV, squark masses of 1 TeV and maximal mixing the upper bound is assumed near tan β ~ 2 and varies between 139.9 and 141.4 GeV. [ABSTRACT FROM AUTHOR]

We motivate, propose and examine a new set of benchmark supersymmetric scenarios, some of which have non-universal Higgs scalar masses (NUHM) and others have gravitino dark matter (GDM). The scalar masses in these proposed models are either considerably larger or smaller than the narrow range allowed for the same gaugino mass m1/2 in the constrained MSSM (CMSSM) with universal scalar masses m0 and neutralino dark matter. Unlike the CMSSM, the proposed NUHM and GDM models with larger m0 may have large branching ratios for Higgs and/or Z production in the cascade decays of heavier sparticles, whose detection we discuss. The novel phenomenology of the GDM models depends on the nature of the next-to-lightest supersymmetric particle (NLSP), which has a lifetime exceeding 104 s in the proposed benchmark scenarios. In one GDM scenario the NLSP is the lightest neutralino χ, and the supersymmetric collider signatures are similar to those in previous CMSSM benchmarks, but with a distinctive spectrum that would be challenging for the LHC and ILC. In the other GDM scenarios based on minimal supergravity (mSUGRA), the NLSP is the lighter stau slepton $\tilde\tau_1$ , with a lifetime between ∼104 and 3×106 s. Every supersymmetric cascade would end in a $\tilde\tau_1$ , which would have a distinctive time-of-flight signature. Slow-moving $\tilde\tau_1$ ’s might be trapped in a collider detector or outside it, and the preferred detection strategy would depend on the $\tilde\tau_1$ lifetime. We discuss the extent to which these mSUGRA GDM scenarios could be distinguished from gauge-mediated models. [ABSTRACT FROM AUTHOR]

We review the present status of the QCD corrected cross-sections and kinematic distributions for the production of a Higgs boson in association with bottom quarks at the Fermilab Tevatron and CERN Large Hadron Collider. Results are presented for the Minimal Supersymmetric Standard Model where, for large tan β, these production modes can be greatly enhanced compared to the Standard Model case. The next-to-leading order QCD results are much less sensitive to the renormalization and factorization scales than the lowest order results, but have a significant dependence on the choice of the renormalization scheme for the bottom quark Yukawa coupling. We also investigate the uncertainties coming from the Parton Distribution Functions and find that these uncertainties can be comparable to the uncertainties from the remaining scale dependence of the next-to-leading order results. We present results separately for the different final states depending on the number of bottom quarks identified. [ABSTRACT FROM AUTHOR]

The top-charm associated productions via e + e-, $e^- \gamma$ and $\gamma \gamma$ collisions at linear colliders, which are extremely suppressed in the standard model (SM), could be significantly enhanced in some extensions of the SM. In this article we calculate the full contribution of the top-color-assisted technicolor (TC2) to these productions and then compare the results with the existing predictions of the SM, the general two-Higgs-doublet model and the minimal supersymmetric model. We find that the TC2 model predicts much larger production rates than other models and the largest-rate channel is $\gamma \gamma \to t \bar{c}$, which exceeds 10 fb for a large part of the parameter space. From the analysis of the observability of such productions at the future linear colliders, we find that the predictions of the TC2 model can reach the observable level for a large part of the parameter space while the predictions of other models are hardly accessible. [ABSTRACT FROM AUTHOR]

Abstract: Non-linearly realized supersymmetry, combined with the Standard Model field content and gauge invariance, permits local dimension-six operators involving a goldstino, a lepton doublet and a Higgs doublet. These interactions preserve total lepton number if the left-handed goldstino transforms as an antilepton. We discuss the resulting phenomenology, in the simple limit where the new couplings involve only one lepton family, thus conserving also lepton flavour. Both the Z boson and the Higgs boson can decay into a neutrino and a goldstino: the present limits from the invisible Z width and from other observables leave room for the striking possibility of a Higgs boson decaying dominantly, or at least with a sizable branching ratio, via such an invisible mode. We finally comment on the perspectives at hadron and lepton colliders, and on possible extensions of our analysis. [Copyright &y& Elsevier]

The DELPHI experiment at the LEP e + e- collider collected almost 700 pb-1 at centre-of-mass energies above the Z0 mass pole and up to 208 GeV. Those data were used to search for SUSY in the Anomaly Mediated SUSY Breaking (AMSB) scenario with a flavour independent common sfermion mass parameter. The searches covered several possible signatures experimentally accessible at LEP, with either the neutralino, the sneutrino or the stau being the Lightest Supersymmetric Particle (LSP). They included: the search for nearly mass-degenerate chargino and neutralino, which is a typical feature of AMSB; the search for Standard-Model-like or invisibly decaying Higgs boson; the search for stable staus; the search for cascade decays of SUSY particles resulting in the LSP and a low multiplicity final state containing neutrinos. No evidence of a signal was found, and thus constraints were set in the space of the parameters of the model. [ABSTRACT FROM AUTHOR]

The Higgs boson search has shifted from LEP2 to the Tevatron and will subsequently move to the LHC. Due to the different initial states, the Higgs production and decay channels relevant for Higgs boson searches are different at hadron colliders compared to LEP2. We suggest new benchmark scenarios for the MSSM Higgs boson search at hadron colliders that exemplify the phenomenology of different parts of the MSSM parameter space. Besides the mhmax scenario and the no-mixing scenario used in the LEP2 Higgs boson searches, we propose two new scenarios. In one scenario the main production channel at the LHC, gg → h, is suppressed over a wide part of the MA-tan Β-plane. In the other scenario, important Higgs decay channels at the Tevatron and at the LHC, h → bb and h → τ+τ- can be suppressed. All scenarios fulfill the LEP2 constraints for nearly the whole MA-tan Β-plane. [ABSTRACT FROM AUTHOR]

A detection at the large hadron collider of a light Higgs pseudoscalar would, if interpreted in a supersymmetric framework, be a smoking gun signature of non-minimal supersymmetry. In this work in the framework of the next-to-minimal supersymmetric standard model we focus on vector boson fusion and Higgs-strahlung production of heavier scalars that subsequently decay into pairs of light pseudoscalars. We demonstrate that although these channels have in general very limited reach, they are viable for the detection of light pseudoscalars in some parts of parameter space and can serve as an important complementary probe to the dominant gluon-fusion production mode. We also demonstrate that in a Higgs factory these channels may reach sensitivities comparable to or even exceeding the gluon fusion channels at the Large Hadron Collider, thus possibly rendering this our best option to discover a light pseudoscalar. It is also worth mentioning that for the singlet dominated scalar this may be the only way to measure its couplings to gauge bosons. Especially promising are channels where the initial scalar is radiated off a W as these events have relatively high rates and provide substantial background suppression due to leptons from the W. We identify three benchmark points that well represent the above scenarios. Assuming that the masses of the scalars and pseudoscalars are already measured in the gluon-fusion channel, the event kinematics can be further constrained, hence significantly improving detection prospects. This is especially important in the Higgs-strahlung channels with rather heavy scalars, and results in possible detection at 200 fb−1 for the most favoured parts of the parameter space. [ABSTRACT FROM AUTHOR]