Observation of the Mass Difference between Neutral Charm-Meson Eigenstates

Self Cite

A combination of measurements sensitive to the CP violation angle γ of the Cabibbo-Kobayashi-Maskawa unitarity triangle and to the charm mixing parameters that describe oscillations between D0 and $$ \overline{D} $$ D ¯ 0 mesons is performed. Results from the charm and beauty sectors, based on data collected with the LHCb detector at CERN’s Large Hadron Collider, are combined for the first time. This method provides an improvement on the precision of the charm mixing parameter y by a factor of two with respect to the current world average. The charm mixing parameters are determined to be $$ x=\left({0.400}_{-0.053}^{+0.052}\right)\% $$ x = 0.400 − 0.053 + 0.052 % and y = $$ \left({0.630}_{-0.030}^{+0.033}\right)\% $$ 0.630 − 0.030 + 0.033 % . The angle γ is found to be γ = $$ \left({65.4}_{-4.2}^{+3.8}\right){}^{\circ} $$ 65.4 − 4.2 + 3.8 ° and is the most precise determination from a single experiment.

Section: Cp Violation In D-meson Decaysmentioning

confidence: 99%

Simultaneous determination of CKM angle γ and charm mixing parameters

Aaij

Abdelmotteleb²,

Beteta³

et al. 2021

Self Cite

“…However, since their contribution is non-perturbative and difficult to compute, there is room for new physics, which in principle can be the dominant contribution to the mass difference ∆m D in D 0 system. In fact, a nonzero mass difference in the D 0 meson system was recently observed by the LHCb collaboration [99]:…”

Section: Jhep10(2021)079mentioning

confidence: 94%

Are the CKM anomalies induced by vector-like quarks? Limits from flavor changing and Standard Model precision tests

Belfatto

Berezhiani

2021

Recent high precision determinations of Vus and Vud indicate towards anomalies in the first row of the CKM matrix. Namely, determination of Vud from beta decays and of Vus from kaon decays imply a violation of first row unitarity at about 3σ level. Moreover, there is tension between determinations of Vus obtained from leptonic Kμ2 and semileptonic Kℓ3 kaon decays. These discrepancies can be explained if there exist extra vector-like quarks at the TeV scale, which have large enough mixings with the lighter quarks. In particular, extra vector-like weak singlets quarks can be thought as a solution to the CKM unitarity problem and an extra vector-like weak doublet can in principle resolve all tensions. The implications of this kind of mixings are examined against the flavour changing phenomena and SM precision tests. We consider separately the effects of an extra down-type isosinglet, up-type isosinglet and an isodoublet containing extra quarks of both up and down type, and determine available parameter spaces for each case. We find that the experimental constraints on flavor changing phenomena become more stringent with larger masses, so that the extra species should have masses no more than few TeV. Moreover, only one type of extra multiplet cannot entirely explain all the discrepancies, and some their combination is required, e.g. two species of isodoublet, or one isodoublet and one (up or down type) isosinglet. We show that these scenarios are testable with future experiments. Namely, if extra vector-like quarks are responsible for CKM anomalies, then at least one of them should be found at scale of few TeV, and anomalous weak isospin violating Z-boson couplings with light quarks should be detected if the experimental precision on Z hadronic decay rate is improved by a factor of 2 or so.

“…New measurements have been provided by the LHCb collaboration allowing for CP violation in mixing and in the interference between mixing and decay. The best fit point is [18]: 1. For future prospects see [19,20].…”

Section: Jhep10(2021)021mentioning

confidence: 97%

The charm of 331

Buras

Colangelo

Fazio

et al. 2021

We perform a detailed analysis of flavour changing neutral current processes in the charm sector in the context of 331 models. As pointed out recently, in the case of Z′ contributions in these models there are no new free parameters beyond those already present in the Bd,s and K meson systems analyzed in the past. As a result, definite ranges for new Physics (NP) effects in various charm observables could be obtained. While generally NP effects turn out to be small, in a number of observables they are much larger than the tiny effects predicted within the Standard Model. In particular we find that the branching ratio of the mode D0→ μ+μ−, despite remaining tiny, can be enhanced by 6 orders of magnitude with respect to the SM. We work out correlations between this mode and rare Bd,s and K decays. We also discuss neutral charm meson oscillations and CP violation in the charm system. In particular, we point out that 331 models provide new weak phases that are a necessary condition to have non-vanishing CP asymmetries. In the case of ∆ACP, the difference between the CP asymmetries in D0→ K+K− and D0→ π+π−, we find that agreement with experiment can be obtained provided that two conditions are verified: the phases in the ranges predicted in 331 models and large hadronic matrix elements.