We review several current aspects of dark matter theory and experiment. We overview the present experimental status, which includes current bounds and recent claims and hints of a possible signal in a wide range of experiments: direct detection in underground laboratories, gamma-ray, cosmic ray, x-ray, neutrino telescopes, and the LHC. We briefly review several possible particle candidates for a weakly interactive massive particle (WIMP) and dark matter that have recently been considered in the literature. We pay particular attention to the lightest neutralino of supersymmetry as it remains the best motivated candidate for dark matter and also shows excellent detection prospects. Finally we briefly review some alternative scenarios that can considerably alter properties and prospects for the detection of dark matter obtained within the standard thermal WIMP paradigm.

WIMP dark matter candidates and searches—current status and future prospects

Motivated by the recent LHC hints of a Higgs boson around 125 GeV, we assume a SM-like Higgs with the mass 123-127 GeV and study its implication in low energy SUSY by comparing the MSSM and NMSSM. We consider various experimental constraints at 2 sigma level (including the muon g - 2 and the dark matter relic density) and perform a comprehensive scan over the parameter space of each model. Then in the parameter space which is allowed by current experimental constraints and also predicts a SM-like Higgs in 123-127 GeV, we examine the properties of the sensitive parameters (like the top squark mass and the trilinear coupling A(t)) and calculate the rates of the di-photon signal and the VV* (V = W, Z) signals at the LHC. Our typical findings are: (i) In the MSSM the top squark and A(t) must be large and thus incur some fine-tuning, which can be much ameliorated in the NMSSM; (ii) In the MSSM a light stau is needed to enhance the di-photon rate of the SM-like Higgs to exceed its SM prediction, while in the NMSSM the di-photon rate can be readily enhanced in several ways; (iii) In the MSSM the signal rates of pp -> h -> VV* at the LHC are never enhanced compared with their SM predictions, while in the NMSSM they may get enhanced significantly; (iv) A large part of the parameter space so far survived will be soon covered by the expected XENON100(2012) sensitivity (especially for the NMSSM).

A SM-like Higgs near 125 GeV in low energy SUSY: a comparative study for MSSM and NMSSM

We review several current aspects of dark matter theory and experiment. We overview the present experimental status, which includes current bounds and recent claims and hints of a possible signal in a wide range of experiments: direct detection in underground laboratories, gamma-ray, cosmic ray, X-ray, neutrino telescopes, and the LHC. We briefly review several possible particle candidates for a Weakly Interactive Massive Particle (WIMP) and dark matter that have recently been considered in the literature. We pay particular attention to the lightest neutralino of supersymmetry as it remains the best motivated candidate for dark matter and also shows excellent detection prospects. Finally we briefly review some alternative scenarios that can considerably alter properties and prospects for the detection of dark matter obtained within the standard thermal WIMP paradigm.

WIMP dark matter candidates and searches - current issues and future prospects

NMSSM Higgs benchmarks near 125 GeV

A natural region in the parameter space of the NMSSM can accomodate a CP-even Higgs boson with a mass of about 125 GeV and, simultaneously, an enhanced cross section times branching ratio in the di-photon channel. This happens in the case of strong singlet-doublet mixing, when the partial width of a 125 GeV Higgs boson into $ b\overline b $
 is strongly reduced. In this case, a second lighter CP-even Higgs boson is potentially also observable at the LHC.

/pdf/a-higgs-boson-near-125-gev-with-enhanced-di-photon-signal-in-4gg1839ah1.pdf

A Higgs boson near 125 GeV with enhanced di-photon signal in the NMSSM

Current experimental constraints on the lightest Higgs boson mass in the constrained MSSM

As a most natural realization of the Next-to Minimal Supersymmetry Standard Model (NMSSM), lambda-SUSY is parameterized by a large lambda around one and a low tan beta below 10. In this work, we first scan the parameter space of lambda-SUSY by considering various experimental constraints, including the limitation from the Higgs data updated by the ATLAS and CMS collaborations in the slimmer of 2014, then we study the properties of the Higgs bosons. We get two characteristic features of lambda-SUSY in experimentally allowed parameter space. One is the triple self coupling of the SM-like Higgs boson may get enhanced by a factor over 10 in comparison with its SM prediction. The other is the pair production of the SM-like Higgs boson at the LHC may be two orders larger than its SM prediction. All these features seems to be unachievable in the Minimal Supersymmetric Standard Model and in the NMSSM with a low lambda. Moreover, we also find that naturalness plays an important role in selecting the parameter space of lambda-SUSY, and that the Higgs X-2 obtained with the latest data is usually significantly smaller than before due to the more consistency of the two collaboration measurmnents.

/pdf/exploring-the-higgs-sector-of-a-most-natural-nmssm-and-its-2xe3q9glkv.pdf

Exploring the Higgs sector of a most natural NMSSM and its prediction on Higgs pair production at the LHC

We investigate the Higgs-strahlung production process e(+)e(-) -> Zh at the future Higgs factory such as TLEP by including radiative corrections in the Minimal Dilaton Model (MDM), which extends the SM by one singlet scalar called dilaton. We consider various theoretical and experimental constraints on the model, and perform fits to the Higgs data taken from ATLAS, CMS and CDF+D0. Then for the 1 sigma surviving samples, we calculate the MDM predictions on the inclusive production rate sigma(e(+)e(-) -> Zh) at the 240-GeV Higgs factory, and also the signal rates of e(+)e(-) -> Zh with the Higgs boson decaying to b (b) over bar and gamma gamma. We have following observations: (1) In the heavy dilaton scenario, the deviation of sigma(e(+)e(-) -> Zh) from its SM prediction can vary from -15% to 85%, which mainly arises from the modification of the tree-level hZZ coupling and also the radiative correction induced by possibly large Higgs self-couplings. (2) The processes e(+)e(-) -> Zh at the Higgs factory and pp -> hh at 14-TeV LHC are complementary in limiting the MDM parameter space. Requiring the deviation of sigma(e(+)e(-) -> Zh) from its SM prediction to be less than 1% and that of sigma(pp -> hh) to be less than 50%, tan theta(S) in the MDM will be limited to be -0.1 vertical bar Zh) may reach -7%, and requiring its size to be less than 1% will result in 0 , R-gamma gamma < 1%.

https://link.springer.com/content/pdf/10.1007%2FJHEP08%282014%29138.pdf

Higgs-strahlung production process e+e− → Zh at the future Higgs factory in the Minimal Dilaton Model

As a most natural realization of the Next-to Minimal Supersymmetry Standard Model (NMSSM), {\lambda}-SUSY is parameterized by a large {\lambda} around one and a low tan$\beta$ below 10. In this work, we first scan the parameter space of {\lambda}-SUSY by considering various experimental constraints, including the limitation from the Higgs data updated by the ATLAS and CMS collaborations in the summer of 2014, then we study the properties of the Higgs bosons. We get two characteristic features of {\lambda}-SUSY in experimentally allowed parameter space. One is the triple self coupling of the SM-like Higgs boson may get enhanced by a factor over 10 in comparison with its SM prediction. The other is the pair production of the SM-like Higgs boson at the LHC may be two orders larger than its SM prediction. All these features seems to be unachievable in the Minimal Supersymmetric Standard Model and in the NMSSM with a low {\lambda}. Moreover, we also find that naturalness plays an important role in selecting the parameter space of {\lambda}-SUSY, and that the Higgs $\chi^2$ obtained with the latest data is usually significantly smaller than before due to the more consistency of the two collaboration measurements.

Exploring the Higgs Sector of a Most Natural NMSSM and its Prediction on Higgs Pair Production at the LHC

We investigate the Higgs-strahlung production process e^+ e^- \to Z h at the future Higgs factory such as TLEP by including radiative corrections in the Minimal Dilaton Model (MDM), which extends the SM by one singlet scalar called dilaton. We consider various theoretical and experimental constraints on the model, and perform fits to the Higgs data taken from ATLAS, CMS and CDF+D0. Then for the 1\sigma surviving samples, we calculate the MDM predictions on the inclusive production rate \sigma(e^+e^-\to Zh) at the 240-GeV Higgs factory, and also the signal rates of e^+e^-\to Zh with the Higgs boson decaying to b\bar b and \gamma\gamma. We have following observations: (1) In the heavy dilaton scenario, the deviation of \sigma(e^+e^-\to Zh) from its SM prediction can vary from -15\% to 85\%, which mainly arises from the modification of the tree-level hZZ coupling and also the radiative correction induced by possibly large Higgs self-couplings. (2) The processes e^+e^-\to Zh at the Higgs factory and pp\to hh at 14-TeV LHC are complementary in limiting the MDM parameter space. Requiring the deviation of \sigma(e^+e^-\to Zh) from its SM prediction to be less than 1\% and that of \sigma(p p \to h h) to be less than 50\%, \tan \theta_S in the MDM will be limited to be -0.1<\tan\theta_S<0.3, and the deviations of the signal rates are constrained to be |R_{b\bar b}|<2\% and |R_{\gamma\gamma}|<7\%. Especially, the Higgs self-coupling normalized to its SM prediction is now upper bounded by about 4. (3) In the light dilaton scenario, the deviation of \sigma(e^+e^-\to Zh) may reach -7\%, and requiring its size to be less than 1\% will result in 0<\tan\theta_S<0.1, and -10\% < R_{b\bar b}, R_{\gamma\gamma} < 1\%.

/pdf/higgs-strahlung-production-process-e-e-to-z-h-at-the-future-3mb4m14cqd.pdf

Dongwei Li

Papers

Current experimental constraints on the lightest Higgs boson mass in the constrained MSSM

Exploring the Higgs sector of a most natural NMSSM and its prediction on Higgs pair production at the LHC

Higgs-strahlung production process e+e− → Zh at the future Higgs factory in the Minimal Dilaton Model

Exploring the Higgs Sector of a Most Natural NMSSM and its Prediction on Higgs Pair Production at the LHC

Higgs-strahlung production process e^+ e^- \to Z h at the future Higgs factory in the Minimal Dilaton Model