Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userGlobal Fits of Third Family Hypercharge Models to Neutral Current B-Anomalies and Electroweak Precision Observables
142
0
0.0
(
0
)
Added by
Jos\\'e Eliel Camargo Molina
Publication date
2021
fields
and research's language is
English
Ask ChatGPT about the research
No Arabic abstract
While it is known that third family hypercharge models can explain the neutral current $B-$anomalies, it was hitherto unclear whether the $Z-Z^prime$ mixing predicted by such models could simultaneously fit electroweak precision observables. Here, we perform global fits of several third family hypercharge models to a combination of electroweak data and those data pertinent to the neutral current $B-$anomalies. While the Standard Model is in tension with this combined data set with a $p-$value of $.00068$, simp
rate research
Read More
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.
We investigate a speculative short-distance force, proposed to explain discrepancies observed between measurements of certain neutral current decays of $B$ hadrons and their Standard Model predictions. The force derives from a spontaneously broken, gauged $U(1)_{B_3-L_2}$ extension to the Standard Model, where the extra quantum numbers of Standard Model fields are given by third family baryon number minus second family lepton number. The only fields beyond those of the Standard Model are three right-handed neutrinos, a gauge field associated with $U(1)_{B_3-L_2}$ and a Standard Model singlet complex scalar which breaks $U(1)_{B_3-L_2}$, a `flavon. This simple model, via interactions involving a TeV scale force-carrying $Z^prime$ vector boson, can successfully explain the neutral current $B-$anomalies whilst accommodating other empirical constraints. In an ansatz for fermion mixing, a combination of up-to-date $B-$anomaly fits, LHC direct $Z^prime$ search limits and other bounds rule out the domain 0.15 TeV$< M_{Z^prime} <$ 1.9 TeV at the 95$%$ confidence level. For more massive $Z^prime$s, the model possesses a {em flavonstrahlung} signal, where $pp$ collisions produce a $Z^prime$ and a flavon, which subsequently decays into two Higgs bosons.
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.
We update the global fit to electroweak precision observables, including the effect of the latest measurements at hadron colliders of the $W$ and top-quark masses and the effective leptonic weak mixing angle. We comment on the impact of these measurements in terms of constraints on new physics. We also update the bounds derived from the fit to the Higgs-boson signal strengths, including the observables measured at the LHC Run 2, and compare the improvements with respect to the 7 and 8 TeV results.
Indirect information about the possible scale of supersymmetry (SUSY) breaking can be obtained from the comparison of precisely measured observables (and also of exclusion limits) with accurate theory predictions incorporating SUSY loop corrections. Recent results are reviewed obtained from a combined analysis of the most sensitive electroweak precision observables (EWPO), M_W, sin^2_theta^eff, Gamma_Z, (g-2)_mu and M_h, and B-physics observables (BPO), BR(b -> s gamma), BR(B_s -> mu^+mu^-), BR(B_u -> tau u_tau) and Delta M_{B_s}. Assuming that the lightest supersymmetric particle (LSP) provides the cold dark matter density preferred by WMAP and other cosmological data, chi^2 fits are performed to the parameters of the constrained minimal supersymmetric extension of the Standard Model (CMSSM), in which the SUSY-breaking parameters are universal at the GUT scale, and the non-universal Higgs model (NUHM), in which this constraint is relaxed for the soft SUSY-breaking contributions to the Higgs masses. Within the CMSSM indirect bounds on the mass of the lightest CP-even Higgs boson are derived.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
