Long-Lived Heavy Quarks: A Review

Abstract

We review the theoretical and experimental situation for long-lived heavy quarks, or bound states thereof, arising in simple extensions of the Standard Model. If these particles propagate large distances before their decay, they give rise to specific signatures requiring dedicated analysis methods. In particular, vector-like quarks with negligible couplings to the three known families could have eluded the past experimental searches. While most analyses assume prompt decays at the production vertex, novel heavy quarks might lead to signatures involving displaced vertices, new hadronic bound states, or decays happening outside of the detector acceptance. We perform reinterpretations of existing searches for short-and long-lived particles, and give suggestions on how to extend their reach to long-lived heavy quarks.

Hadronic and Hadron-Like Physics of Dark Matter

“…Most of the two-and three-quark states, which are represented in Table I, were considered also in Refs. [20,51]. Ref.…”

Dark Matter in the Standard Model Extension with Singlet Quark

“…Note, these limits are much less then the estimation of quark mass which follows from the DM analysis (see the fourth section). Theoretical and experimental situation for long-lived heavy quarks was considerably discussed in the review [10], where it was noted that vector-like new heavy quarks can elude experimental contraints from LHC.…”

“…Characteristics of U-type hadrons Table 1 were also considered in Ref. [10] for the case of long-lived vector-like heavy quark and in Ref. [29], where U-type quark belong to the sequential 4-th generation.…”

Survey of vector-like fermion extensions of the Standard Model and their phenomenological implications

“…Heavy charged long-lived states such as these usually have low, but not zero, energy loss in the detector and may charge oscillate. Limits on longlived VL quarks can be derived from the interpretation of ATLAS and CMS searches [86]. Using CMS results [87] one can exclude m Q < 800 GeV for cτ > 3m, assuming behaviour similar to that of long-lived heavy scalar top quarks.…”

“…Using CMS results [87] one can exclude m Q < 800 GeV for cτ > 3m, assuming behaviour similar to that of long-lived heavy scalar top quarks. A caveat is that these limits assume pair-production of the VL quarks, with kinematics independent of the lifetime of the particle [86]. The MoEDAL collaboration discusses [88] in more detail the limits on production cross-section-dependent limits for various decay lifetimes of long-lived VL quarks.…”