Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userHadron Collider Sensitivity to Fat Flavourful $Z^prime$s for $R_{K^{(ast)}}$
90
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We further investigate the case where new physics in the form of a massive $Z^prime$ particle explains apparent measurements of lepton flavour non-universality in $B rightarrow K^{(ast)} l^+ l^-$ decays. Hadron collider sensitivities for direct production of such $Z^prime$s have been previously studied in the narrow width limit for a $mu^+ mu^-$ final state. Here, we extend the analysis to sizeable decay widths and improve the sensitivity estimate for the narrow width case. We estimate the sensitivities of the high luminosity 14 TeV Large Hadron Collider (HL-LHC), a high energy 27 TeV LHC (HE-LHC), as well as a potential 100 TeV future circular collider (FCC). The HL-LHC has sensitivity to narrow $Z^prime$ resonances consistent with the anomalies. In one of our simplified models the FCC could probe 23 TeV $Z^prime$ particles with widths of up to 0.35 of their mass at 95% confidence level (CL). In another model, the HL-LHC and HE-LHC cover sizeable portions of parameter space, but the whole of perturbative parameter space can be covered by the FCC.
rate research
Read More
We show how any flavour conserving $Z$ model can be made flavour violating and non-universal by introducing mass mixing of quarks and leptons with a fourth family of vector-like fermions with non-universal $Z$ couplings. After developing a general formalism, we focus on two concrete examples, namely a fermiophobic model, and an $SO(10)$ GUT model, and show how they can account for the anomalous $B$ decay ratios $R_K$ and $R_{K^*}$. A similar analysis could be performed for $B-L$ models, $E_6$ models, composite models, and so on.
The LHCb measurements of the $mu / e$ ratio in $B to K ell ell$ decays $(R_{K^{}})$ indicate a deficit with respect to the Standard Model prediction, supporting earlier hints of lepton universality violation observed in the $R_{K^{(*)}}$ ratio. Possible explanations of these $B$-physics anomalies include heavy $Z$ bosons or leptoquarks mediating $b to s mu^+ mu^- $. We note that a muon collider can directly measure this process via $mu^+ mu^- to b bar s$ and can shed light on the lepton non-universality scenario. Investigating currently discussed center-of-mass energies $sqrt{s} = 3$, 6 and 10 TeV, we show that the parameter space of $Z$ and $S_3$ leptoquark solutions to the $R_{K^{(*)}}$ anomalies can be mostly covered. Effective operators explaining the anomalies can be probed with the muon collider setup $sqrt{s} = 6~{rm TeV}$ and integrated luminosity $L = 4~{rm ab^{-1}}$.
We present a model to explain LHCbs recent measurements of $R_K$ and $R_{K^{ast}}$ based on an anomaly-free, spontaneously-broken $U(1)_F$ gauge symmetry, without any fermionic fields beyond those of the Standard Model (SM). The model explains the hierarchical heaviness of the third family and the smallness of quark mixing. The $U(1)_F$ charges of the third family of SM fields and the Higgs doublet are set equal to their respective hypercharges. A heavy $Z^prime$ particle with flavour-dependent couplings can modify the $[overline{b_L} gamma^rho s_L][overline{mu_L} gamma_rho mu_L]$ effective vertex in the desired way. The $Z^prime$ contribution to $B_s-overline{B_s}$ mixing is suppressed by a small mixing angle connected to $V_{ts}$, making the constraint coming from its measurement easier to satisfy. The model can explain $R_K$ and $R_{K^{(ast)}}$ whilst simultaneously passing other constraints, including measurements of the lepton flavour universality of $Z$ couplings.
The flavorful $Z^prime$ model with its couplings restricted to the left-handed second generation leptons and third generation quarks can potentially resolve the observed anomalies in $R_K$ and $R_{K^*}$. After examining the current limits on this model from various low-energy processes, we probe this scenario at 14 TeV high-luminosity run of the LHC using two complementary channels: one governed by the coupling of $Z$ to $b$-quarks and the other to muons. We also discuss the implications of the latest LHC high mass resonance searches in the dimuon channel on the model parameter space of our interest.
We examine current collider constraints on some simple $Z^prime$ models that fit neutral current $B-$anomalies, including constraints coming from measurements of Standard Model (SM) signatures at the LHC. The `MDM simplified model is not constrained by the SM measurements but {em is} strongly constrained by a 139 fb$^{-1}$ 13 TeV ATLAS di-muon search. Constraints upon the `MUM simplified model are much weaker. A combination of the current $B_s$ mixing constraint and ATLAS $Z^prime$ search implies $M_{Z^prime}>1.2$ TeV in the Third Family Hypercharge Model example case. LHC SM measurements rule out a portion of the parameter space of the model for $M_{Z^prime}<1.5$ TeV.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
