Higgs-Radion interpretation of the LHC data?
We explore the parameter choices in the five-dimensional Randall-Sundrum model with the inclusion of Higgs-radion mixing that can describe current LHC hints for one or more Higgs boson signals.
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arXiv subjects
John F. Gunion
Publications and source records attributed to John F. Gunion.
The constrained NMSSM and Higgs near 125 GeV
We assess the extent to which various constrained versions of the NMSSM are able to describe the recent hints of a Higgs signal at the LHC corresponding to a Higgs mass in the range 123-128 GeV.
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CoGeNT, DAMA, and Light Neutralino Dark Matter
Recent observations by the CoGeNT collaboration (as well as long standing observations by DAMA/LIBRA) suggest the presence of a $\sim 5$-10 GeV dark matter particle with a somewhat large elastic scattering cross section with nucleons ($σ\sim 10^{-40}$ cm$^2$).Within the context of the minimal supersymmetric standard model (MSSM), neutralinos in this mass range are not able to possess such large cross sections, and would be overproduced in the early universe. Simple extensions of the MSSM, however, can easily accommodate these observations. In particular, the extension of the MSSM by a chiral singlet superfield allows for the possibility that the dark matter is made up of a light singlino that interacts with nucleons largely through the exchange of a fairly light ($\sim$30-70 GeV) singlet-like scalar higgs, $\hi$. Such a scenario is consistent with all current collider constraints and can generate the signals reported by CoGeNT and DAMA/LIBRA. Furthermore, there is a generic limit of the extended model in which there is a singlet-like pseudoscalar higgs, $\ai$, with $\mai\sim \mhi$ and in which the $χ^0χ^0$ and $b\anti b, s\anti s$ coupling magnitudes of the $\hi$ and $\ai$ are very similar. In this case, the thermal relic abundance is automatically consistent with the measured density of dark matter if $\mchi$ is sufficiently small that $χ^0χ^0\to b\anti b$ is forbidden.
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Next-to-Minimal Supersymmetric Model Higgs Scenarios for Partially Universal GUT Scale Boundary Conditions
We examine the extent to which it is possible to realize the NMSSM "ideal Higgs" models espoused in several papers by Gunion et al in the context of partially universal GUT scale boundary conditions. To this end we use the powerful methodology of nested sampling. We pay particular attention to whether ideal-Higgs-like points not only pass LEP constraints but are also acceptable in terms of the numerous constraints now available, including those from the Tevatron and $B$-factory data, $(g-2)_μ$ and the relic density $Ωh^2$. In general for this particular methodology and range of parameters chosen, very few points corresponding to said previous studies were found, and those that were found were at best $2σ$ away from the preferred relic density value. Instead, there exist a class of points, which combine a mostly singlet-like Higgs with a mostly singlino-like neutralino coannihilating with the lightest stau, that are able to effectively pass all implemented constraints in the region $80<m_h<100$. It seems that the spin-independent direct detection cross section acts as a key discriminator between ideal Higgs points and the hard to detect singlino-like points.
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A two-Higgs-doublet interpretation of a small Tevatron $Wjj$ excess
We show that a $Wjj$ excess in Tevatron data could be explained in the context of the standard non-supersymmetric two-Higgs-doublet model for appropriately chosen parameters. Correlated signals in the $γγ$ and $W^+ W^- b \anti b$ final states are predicted and are on the verge of being detectable. The proposed model is most attractive if the cross section for the $Wjj$ excess is $\lsim 1-2\pb$.
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Ruling out a 4th generation using limits on hadron collider Higgs signals
We consider the impact of a 4th generation on Higgs to $γγ$ and $WW,ZZ$ signals and demonstrate that the Tevatron and LHC have essentially eliminated the possibility of a 4th generation if the Higgs is SM-like and has mass below 200 GeV. We also show that the absence of enhanced Higgs signals in current data sets in the $γγ$ and $WW,ZZ$ final states can strongly constrain the possibility of a 4th generation in two-Higgs-doublet models of type II, including the MSSM.
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The Higgs Sector and CoGeNT/DAMA-Like Dark Matter in Supersymmetric Models
Recent data from CoGeNT and DAMA are roughly consistent with a very light dark matter particle with $m\sim 4-10\gev$ and spin-independent cross section of order $σ_{SI} \sim (1-3)\times 10^{-4}\pb$. An important question is whether these observations are compatible with supersymmetric models obeying $Ωh^2\sim 0.11$ without violating existing collider constraints and precision measurements. In this talk, I review the fact the the Minimal Supersymmetric Model allows insufficient flexibility to achieve such compatibility, basically because of the highly constrained nature of the MSSM Higgs sector in relation to LEP limits on Higgs bosons. I then outline the manner in which the more flexible Higgs sectors of the Next-to-Minimal Supersymmetric Model and an Extended Next-to-Minimal Supersymmetric Model allow large $σ_{SI}$ and $Ωh^2\sim 0.11$ at low LSP mass without violating LEP, Tevatron, BaBar and other experimental limits. The relationship of the required Higgs sectors to the NMSSM "ideal-Higgs" scenarios is discussed.
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CoGeNT, DAMA, and Neutralino Dark Matter in the Next-To-Minimal Supersymmetric Standard Model
We assess the extent to which the NMSSM can allow for light dark matter in the $2\gev\lsim \mcnone\lsim 12\gev$ mass range with correct relic density and large spin-independent direct-detection cross section, $\sigsi$, in the range suggested by \cogent\ and DAMA. For standard assumptions regarding nucleon $s$-quark content and cosmological relic density, $ρ$, we find that the NMSSM falls short by a factor of about 10 to 15 (3 to 5) without (with) significant violation of the current $(g-2)_μ$ constraints.
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Accurate Mass Determinations in Decay Chains with Missing Energy: II
We discuss kinematic methods for determining the masses of the particles in events at a hadron collider in which a pair of identical particles is produced with each decaying via a series of on-shell intermediate beyond-the-SM (BSM) particles to visible SM particles and an invisible particle (schematically, pp -> ZZ + jets with Z -> Aa -> Bba -> Ccba -> ... -> cba... + N where a,b,c,... are visible SM particles or groups of SM particles, A,B,C,... are on-shell BSM particles and N is invisible). This topology arises in many models including SUSY processes such as squark and gluino pair production and decay. We present the detailed procedure for the case of Z -> 3 visible particles + N and demonstrate that the masses obtained from the kinematic procedure are independent of the model by comparing SUSY to UED.
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Direct production of a light CP-odd Higgs boson at the Tevatron and LHC
We show that the existing CDF $L=630 pb^{-1}$ Tevatron data on $pp\to μ^+μ^- + X$ places substantial limits on a light CP-odd Higgs boson $a$ with $m_a<2m_B$ produced via $gg\to a$, even for $m_a>2m_τ$ for which $BR(a\to μ^+μ^-)$ is relatively small. Extrapolation of this existing CDF analysis to $L=10 fb^{-1}$ suggests that Tevatron limits on the $a b\anti b$ coupling strength in the region $m_a>8\gev$ could be comparable to or better than limits from Upsilon decays in the $m_a<7\gev$ region. We also give rough estimates of future prospects at the LHC, demonstrating that early running will substantially improve limits on a light $a$ (or perhaps discover a signal). In particular, outside the Upsilon peak region, integrated luminosity of only $5-20 fb^{-1}$ (depending on $m_a$ and $\sqrt s$) could reveal a peak in $M_{μ^+μ^-}$ and will certainly place important new limits on a light $a$. The importance of such limits in the context of NMSSM Higgs discovery and $(g-2)_μ$ are outlined.
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New constraints on a light CP-odd Higgs boson and related NMSSM Ideal Higgs Scenarios
Recent BaBar limits on $\br(Υ(3S)\to \gam a\to \gam τ^+τ^-)$ and $\br(Υ(3S)\to \gam a\to \gam μ^+μ^-)$ provide increased constraints on the $a b\anti b$ coupling of a CP-odd Higgs boson, $a$, with $m_a 7.5\gev$ scenarios, which are theoretically the most favored, survive. We also outline the impact of the new ALEPH LEP results in the $\epem\to Z+4τ$ channel. For $\tanβ\geq 3$, only NMSSM ideal Higgs scenarios with $m_{h_1}\gsim 98\gev$ and $m_{a_1}$ close to $2m_B $ satisfy the ALEPH limits. For $\tanβ\lsim 2$, the ALEPH limits are easily satisfied for the most theoretically preferred NMSSM scenarios, which are those with $m_{a_1}$ close to $2m_B$ and $m_{h_1}\sim 90\gev-100\gev$.
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Invisible Higgs Decays from Higgs Graviscalar Mixing
We recompute the invisible Higgs decay width arising from Higgs-graviscalar mixing in the ADD model, comparing the original derivation in the non-diagonal mass basis to that in a diagonal mass basis. The results obtained are identical (and differ by a factor of 2 from the original calculation) but the diagonal-basis derivation is pedagogically useful for clarifying the physics of the invisible width from mixing. We emphasize that both derivations make it clear that a direct scan in energy for a process such as $WW\to WW$ mediated by Higgs plus graviscalar intermediate resonances would follow a {\it single} Breit-Wigner form with total width given by $Γ^{tot}=Γ_h^{SM}+Γ_{invisible}$. We also compute the additional contributions to the invisible width due to direct Higgs to graviscalar pair decays. We find that the invisible width due to the latter is relatively small unless the Higgs mass is comparable to or larger than the effective extra-dimensional Planck mass.
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A light CP-odd Higgs boson and the muon anomalous magnetic moment
We amalgamate the many experimental limits on the $ab\anti b$ coupling of a light CP-odd Higgs boson, $a$, including model-dependence coming from the ratio of the $at\anti t$ to the $a b\anti b$ coupling. We then employ these limits to analyze the extent to which a light $a$ can make a significant contribution to the discrepancy, $Δa_μ$, between the experimentally observed $a_μ$ and that predicted by the standard model. In a "model-independent" framework and in the context of a general two-Higgs-doublet model this is a significant possibility. In contrast, the minimal supersymmetric model is too strongly constrained (after combining experimental and theoretical input) to allow a CP-odd-$a$ explanation of $Δa_μ$. The next-to-minimal supersymmetric model allows more freedom and the light $a$ of the model could explain the full $Δa_μ$ if $9.2\gev<\ma<12\gev $, or contribute substantially for larger $\ma$, if $\tanb$ is large.
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Many Light Higgs Bosons in the NMSSM
The next-to-minimal supersymmetric model with a light doublet-like CP-odd Higgs boson and small $\tan β$ can satisfy all experimental limits on Higgs bosons even with light superpartners. In these scenarios, the two lightest CP-even Higgs bosons, $\hi$ and $\hii$, and the charged Higgs boson, $\hp$, can all be light enough to be produced at LEP and yet have decays that have not been looked for or are poorly constrained by existing collider experiments. The channel $\hi\to \ai\ai$ (where $\ai$ is the lightest CP-odd boson and has mass below $2m_b$) with $\ai\to τ^+τ^-$ or $2j$ is still awaiting LEP constraints for $\mhi>86\gev$ or $82\gev$, respectively. LEP data may also contain $\epem\to \hii\ai$ events where $\hii\to Z\ai$ is the dominant decay, a channel that was never examined. Decays of the charged Higgs bosons are often dominated by $H^\pm \to W^{\pm (\star)} \ai$ with $\ai \to gg,c \bar c, τ^+ τ^-$. This is a channel that has so far been ignored in the search for $t\to \hp b$ decays at the Tevatron. A specialized analysis might reveal a signal. The light $\ai$ might be within the reach of $B$ factories via $Υ\to γ\ai$ decays. We study typical mass ranges and branching ratios of Higgs bosons in this scenario and compare these scenarios where the $\ai$ has a large doublet component to the more general scenarios with arbitrary singlet component for the $\ai$.
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New (and Old) Perspectives on Higgs Physics
Old and new ideas regarding Higgs physics are reviewed. We first summarize the quadratic divergence / hierarchy problem which strongly suggests that the SM Higgs sector will be supplemented by new physics at high scales. We next consider means for delaying the hierarchy problem of the SM Higgs sector to unexpectedly high scales. We then outline the properties of the most ideal Higgs boson. The main advantages of a supersymmetric solution to the high scale problems are summarized and the reasons for preferring the next-to-minimal supersymmetric model over the minimal supersymmetric model in order to achieve an ideal Higgs are emphasized. This leads us to the strongly motivated scenario in which there is a Higgs $h$ with SM-like $WW,ZZ$ couplings and $\mh\sim 100\gev$ that decays via $h\to aa$ with $m_a<2m_b$, where $m_a>2m_τ$ is preferred, implying $a\to τ^+ τ^-$. The means for detecting an $h\to aa\to 4τ$ signal are then discussed. Some final cautionary and concluding remarks are given.
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Accurate Mass Determinations in Decay Chains with Missing Energy
Many beyond the Standard Model theories include a stable dark matter candidate that yields missing / invisible energy in collider detectors. If observed at the Large Hadron Collider, we must determine if its mass and other properties (and those of its partners) predict the correct dark matter relic density. We give a new procedure for determining its mass with small error.
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Nonstandard Higgs Boson Decays
This review summarizes the motivations for and phenomenological consequences of nonstandard Higgs boson decays, with emphasis on final states containing a pair of non-Standard-Model particles that subsequently decay to Standard Model particles. Typically these non-Standard-Model particles are part of a ``hidden'' sector, for example a pair of neutral Higgs bosons or a pair of unstable neutralinos. We emphasize that such decays allow for a Higgs substantially below the Standard Model Higgs LEP limit of 114 GeV. This in turn means that the ``fine-tuning'' problems of many Beyond the Standard Model (BSM) theories, in particular supersymmetric models, can be eliminated while achieving excellent consistency with precision electroweak data which favor a Higgs boson with mass below $100\gev$ and standard $WW$, $ZZ$, and top couplings.
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Mass Determination in SUSY-like Events with Missing Energy
We describe a kinematic method which is capable of determining the overall mass scale in SUSY-like events at a hadron collider with two missing (dark matter) particles. We focus on the kinematic topology in which a pair of identical particles is produced with each decaying to two leptons and an invisible particle (schematically, $pp\to YY+jets$ followed by each $Y$ decaying via $Y\to \ell X\to \ell\ell'N$ where $N$ is invisible). This topology arises in many SUSY processes such as squark and gluino production and decay, not to mention $t\anti t$ di-lepton decays. In the example where the final state leptons are all muons, our errors on the masses of the particles $Y$, $X$ and $N$ in the decay chain range from 4 GeV for 2000 events after cuts to 13 GeV for 400 events after cuts. Errors for mass differences are much smaller. Our ability to determine masses comes from considering all the kinematic information in the event, including the missing momentum, in conjunction with the quadratic constraints that arise from the $Y$, $X$ and $N$ mass-shell conditions. Realistic missing momentum and lepton momenta uncertainties are included in the analysis.
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