[论文解读] The Hunt for the Rest of the Higgs Bosons

Nathaniel Craig, Francesco D’Eramo+3 more|arXiv (Cornell University)|Apr 17, 2015

Particle physics theoretical and experimental studies参考文献 64被引用 8

一句话总结

本文 identifies three critical LHC search channels for discovering additional Higgs bosons beyond the Standard Model: (1) production of a heavy scalar or pseudoscalar decaying to top quarks, (2) associated production of a heavy Higgs with $b\bar{b}$ or invisible decays, and (3) $t\bar{b}$ associated production of a charged Higgs decaying to $\bar{t}b$. These channels provide robust coverage of single production modes in extended Higgs sectors, especially under the constraint of alignment limit scenarios where the 125 GeV Higgs closely resembles the SM Higgs.

ABSTRACT

We assess the current state of searches at the LHC for additional Higgs bosons in light of both direct limits and indirect bounds coming from coupling measurements of the Standard Model-like Higgs boson. Given current constraints, we identify and study three LHC searches that are critical components of a comprehensive program to investigate extended electroweak symmetry breaking sectors: production of a heavy scalar or pseudoscalar with decay to $t \bar t$; $b \bar b$ and $t \bar t$ associated production of a heavy scalar or pseudoscalar with decay to invisible final states; and $t \bar b$ associated production of a charged Higgs with decay to $\bar t b$. Systematic experimental searches in these channels would contribute to robust coverage of the possible single production modes of additional heavy Higgs bosons.

研究动机与目标

• To identify the most sensitive and comprehensive LHC search channels for additional Higgs bosons in extended electroweak symmetry breaking sectors.
• To address the gap in current searches that miss Higgs bosons with suppressed couplings to SM gauge bosons or fermions, especially in alignment limit scenarios.
• To guide future LHC Run 2 searches by prioritizing signatures that systematically cover single production modes of heavy Higgs states.
• To leverage coupling measurements of the 125 GeV Higgs boson to constrain and guide the search strategy for new Higgs states.
• To ensure robust coverage of parameter space in models like the 2HDM and real singlet extensions, where new Higgs bosons may evade standard search modes.

提出的方法

• Classify potential Higgs search signatures using simplified models, focusing on single additional Higgs states with SM fermion and boson final states.
• Use the alignment limit as a theoretical guide, where the 125 GeV Higgs is nearly SM-like, to constrain couplings of additional Higgs bosons.
• Analyze production and decay modes of heavy Higgs bosons under the assumption of suppressed couplings to SM gauge bosons (e.g., in real singlet or 2HDM models).
• Focus on three key LHC search channels: $pp \to H/A \to t\bar{t}$, $pp \to H/A \to b\bar{b} + \text{invisible}$, and $pp \to H^\pm \to t\bar{b}$, which are sensitive to different coupling structures.
• Apply kinematic reconstruction techniques to top quarks and $W$ bosons, including solving for neutrino momentum using mass-shell constraints and $m_W$ and $m_t$ on-shell conditions.
• Use a $\chi^2$ minimization strategy over all possible $W$ and $b$-jet combinations to select the best top quark reconstruction, with $\sigma_h = 50$ GeV and $\sigma_\ell = 25$ GeV for uncertainties.

实验结果

研究问题

• RQ1 Which LHC search channels are most effective for discovering additional Higgs bosons when their couplings to SM gauge bosons are suppressed?
• RQ2 How do coupling measurements of the 125 GeV Higgs boson constrain the parameter space of extended Higgs sectors, particularly in the alignment limit?
• RQ3 What are the dominant production and decay modes of additional Higgs bosons in models like the 2HDM and real singlet extension under alignment limit conditions?
• RQ4 How can kinematic reconstruction techniques improve the sensitivity to top quark and $W$ boson decays in events with missing transverse momentum?
• RQ5 What systematic improvements are needed in LHC searches to ensure coverage of Higgs bosons that evade standard search channels due to suppressed or invisible decays?

主要发现

• The $pp \to H/A \to t\bar{t}$ channel is a critical probe for heavy Higgs bosons with significant couplings to top quarks, especially when couplings to $W$ and $Z$ bosons are suppressed.
• The $pp \to H/A \to b\bar{b} + \text{invisible}$ channel provides strong sensitivity to Higgs bosons decaying to invisible final states, particularly in models with a real singlet or extended scalar sector.
• The $pp \to H^\pm \to t\bar{b}$ channel is essential for discovering charged Higgs bosons, especially in models like 2HDM where such decays are kinematically allowed and potentially dominant.
• Kinematic reconstruction of top quarks using $W$ mass-shell and $m_t$ on-shell constraints achieves high efficiency, with over 85% of reconstructed top quarks having $\delta p/E < 0.15$ in the rest frame.
• For events with no real solution for neutrino momentum, a small correction of order 1% to the missing transverse momentum is sufficient to restore a physical solution, minimizing reconstruction bias.
• The $\chi^2$-based reconstruction method effectively selects the correct top quark combination, with the best-fit solution minimizing deviations from the true top quark mass of 173.2 GeV.