Implications of a 125 GeV Higgs scalar for LHC SUSY and neutralino dark matter searches (1112.3017v3)

Abstract: The ATLAS and CMS collaborations have reported an excess of events in the \gamma\gamma, ZZ^*\to 4\ell and WW^* search channels at an invariant mass m \simeq 125 GeV, which could be the first evidence for the long-awaited Higgs boson. We investigate the consequences of requiring m_h\simeq 125 GeV in both the mSUGRA and NUHM2 SUSY models. In mSUGRA, large values of trilinear soft breaking parameter |A_0| are required, and universal scalar m_0\agt 0.8 TeV is favored so that we expect squark and slepton masses typically in the multi-TeV range. This typically gives rise to an "effective SUSY" type of sparticle mass spectrum. In this case, we expect gluino pair production as the dominant sparticle creation reaction at LHC. For m_0< 5 TeV, the superpotential parameter \mu > 2 TeV and m_A> 0.8 TeV, greatly restricting neutralino annihilation mechanisms. These latter conclusions are softened if m_0\sim 10-20 TeV or if one proceeds to the NUHM2 model. The standard neutralino abundance tends to be far above WMAP-measured values unless the neutralino is higgsino-like. We remark upon possible non-standard (but perhaps more attractive) cosmological scenarios which can bring the predicted dark matter abundance into accord with the measured value, and discuss the implications for direct and indirect detection of neutralino cold dark matter.

• The paper investigates the implications of a 125 GeV Higgs boson for searches of supersymmetry (SUSY) and neutralino dark matter within mSUGRA and NUHM2 models.
• The research finds that a 125 GeV Higgs demands large scalar masses in mSUGRA, pushing squarks and sleptons into the multi-TeV range and favoring decoupled spectra for LHC searches.
• The study discusses neutralino dark matter viability, suggesting alternative cosmologies might be needed for consistency with observations and highlighting the flexibility of the NUHM2 model.

Overview of Higgs Scalar Implications for SUSY and Neutralino Dark Matter Searches

The paper, authored by Baer, Barger, and Mustafayev, investigates the implications of a 125 GeV Higgs boson on searches for supersymmetry (SUSY) and neutralino dark matter within the frameworks of mSUGRA and NUHM2 models. With recent reports from ATLAS and CMS collaborations indicating a Higgs boson mass around 125 GeV, the paper provides a focused exploration of the consequences for SUSY parameter spaces, dark matter detection, and related phenomenological contexts.

Main Findings and Numerical Insights

The research reveals several key insights:

1. Constraints on mSUGRA Parameters: A Higgs mass of 125 GeV demands large scalar masses (m_0), generally exceeding 0.8 TeV, thereby pushing squark and slepton masses into the multi-TeV range. It is noted that a significant portion of the mSUGRA parameter space is excluded or severely constrained, particularly requiring that |A_0| ≳ 1.8 × m_0. This favors a decoupled spectrum where gauginos are comparatively light, suggesting gluino pair production might be the dominant SUSY particle process at LHC.
2. Neutralino Dark Matter Viability: The paper discusses scenarios for achieving a WMAP-consistent neutralino dark matter abundance. Traditional cosmological models generally predict an overabundance unless the neutralino is higgsino-like. This suggests alternative cosmologies, such as those involving axinos or moduli fields, could reconcile theoretical predictions with observed values.
3. NUHM2 Model Advantages: The NUHM2 model offers more flexibility compared to mSUGRA, particularly with relaxed constraints on μ and m_A, allowing a broader range of parameter combinations that accommodate a 125 GeV Higgs. It also supports configurations where the neutralino remains a viable dark matter candidate across different cosmological scenarios.
4. Non-standard Cosmological Scenarios: The paper explores models that incorporate late-decaying moduli fields or axinos as a mechanism to mitigate the overabundance of neutralinos. These suggestions highlight the potential necessity of revising standard cosmological assumptions to align theoretical predictions with empirical data.
5. Implications for Rare Decay Processes: The research assesses the impact of a 125 GeV Higgs on processes such as (g-2)_μ, BF(b → sγ), and BF(B_s → μ^+μ^-). It concludes that while the Higgs mass challenges the anomalous magnetic moment discrepancies, it remains broadly consistent with measurements of rare B decays.

Theoretical and Practical Implications

The implications of this research are substantial for the field of particle physics, particularly in refining SUSY and dark matter search strategies at high-energy colliders like the LHC. A 125 GeV Higgs complicates the landscape of SUSY parameter space, emphasizing models that predict substantial splitting between gaugino and scalar masses. It also necessitates contemplation of non-standard cosmological models to achieve measured dark matter relic densities. Furthermore, the findings underscore the challenges in aligning SUSY-derived predictions with observed phenomena such as the muon g-2 anomaly.

Future Directions

The research opens avenues for further examination of non-standard cosmological theories that can potentially bridge gaps between theoretical predictions and empirical data, particularly regarding neutralino dark matter. Moreover, as LHC continues to accumulate data, ongoing SUSY searches will benefit from the constraints and predictions highlighted, focusing efforts on feasible signatures corresponding to large scalar mass scenarios and higgsino-like neutralinos.

In summary, Baer, Barger, and Mustafayev's paper offers a rigorous analysis of how a 125 GeV Higgs impacts SUSY characteristics and strategies for neutralino dark matter detection while simultaneously providing a framework for considering alternative cosmological models.