I discuss hadronic decays of $D$ mesons with emphasis on the recent discovery of charm CP violation in $D^0\to K^+K^-,π^+π^-$ decays. The measured difference $Δa_{CP} \, \equiv \; a_{CP}^{\mathrm{dir}}(D^0\rightarrow K^+K^-) - a_{CP}^{\mathrm{dir}}(D^0\rightarrowπ^+π^-) = \; (-15.4\pm 2.9)\cdot 10^{-4}$ of two direct CP asymmetries exceeds the SM prediction by a factor of 7. A possible explanation is an enhancement of the penguin amplitude entering $ a_{CP}^{\mathrm{dir}}$ by QCD effects which are not understood yet. Alternatively, $Δa_{CP}$ could be dominated by contributions from new physics. In order to distinguish these two hypotheses further CP asymmetries should be measured. To this end CP asymmetries resulting from the interference of two tree-level amplitudes auch as $a_{CP}^{\mathrm{dir}}(D^0\rightarrow K_SK_S)$ or $a_{CP}^{\mathrm{dir}}(D^0 \to K^{*0} K_S)$ are especially interesting.
The importance of charm decays in the context of flavor is motivated. A theory overview on recent developments in leptonic and semileptonic decays, hadronic two-body decays, and rare decays is presented. Standard Model (SM) predictions as well as tests of the SM are pointed out, {\it e.g.}~how to discover direct CP violation in charm decays and how to search for physics beyond the SM. Differences between rare charm and beauty decays are discussed.
We study rare decays of Charm in NSIs. We calculate the NSIs Branching ratios of these decays. There is a strong dependence of these on new physics parameter. They provide, stringent constraints on free parameter in tau.
An analysis of charm mesons decaying semileptonically via Flavor Changing Neutral Currents is presented. We calculate the Wilson coefficients within the Standard Model. A window in the decay distribution, where physics beyond the Standard Model could be measured is identified. Exemplary, we study effects of leptoquark models.
Evading the CKM Hierarchy: Intrinsic Charm in B Decays
我们表明，强子的光锥波函数中的内禀魅力的存在，即使在百分之几的水平，提供了新的，竞争性的衰变机制B衰变名义上CKM抑制。例如，由于CKM抑制了树能级的b \to s u \bar u衰变，所以B介子到由奇异轻强子组成的二体排他态（如B \to π K）的弱衰变将被企鹅贡献所支配.然而，较高的Fock态的B波函数包含的魅力夸克对可以介导的衰变通过CKM-青睐的b \to s c \bar c树能级跃迁。这种内在魅力的贡献可以是现象学上的重要。由于它们模仿了“迷人”企鹅贡献的振幅结构，迷人的企鹅根本不需要是企鹅。
In this work, we investigate the $X(3915)$ and $Z(3930)$ decays into $J/ψω$ with the $χ_{c0}^\prime(2P)$ and $χ_{c2}^\prime (2P)$ assignments to $X(3915)$ and $Z(3930)$, respectively. The results show that the decay width of $Z(3930)\to J/ψω$ is at least one order smaller than that of $X(3915)\to J/ψω$. This observation explains why only one structure $X(3915)$ has been observed in the $J/ψω$ invariant mass spectrum for the process $γγ\to J/ψω$.
The nonleptonic decays of $Ξ_c^0$ and $Λ_c^+$ that are dominated by $W$-exchange are studied. In particular, we anlayse the decay modes $Ξ_c^0 \rightarrow Ξ^{*-} π^+, Σ^{*+}K^-, Ω^-K^+$ and $Λ_c^+\rightarrow Σ^0π^+, Ξ^0 K^+$, $Ξ^0_c\rightarrow Σ^+K^-$.
This is an extension of the prediction of strange baryon decays to the decays of charmed baryons using QCD Sum Rules. Using QCD Sum Rules we estimate the decay $Λ^+_c (udc) \rightarrow Λ^o_s(uds)+ π^+$. Although some weak decays of the $Λ^+_c$ have been measured, since it is difficult to measure $Λ^+_c \rightarrow Λ^o_s+ π^+$ our estimates should be useful for future experiments
LCSR analysis of exclusive two-body B decay into charmonium
我们分析了B -> K H_c（其中H_c = eta_c，J/psi，chi_{cJ(J=0,1)}）衰变，估计了光锥求和规则（LCSR）的不可因式分解贡献.对于B -> K J/psi，特别是对于B -> K chi_{c1}衰变，不可因式分解的贡献是相当大的。对于B衰变成一个（伪）标量charmonia，我们发现小的nonfactorizable的贡献，不能容纳相对较大的分支比的测量。这特别关系到令人困惑的B -> K chi_{c0}衰变。
Leptonic and semileptonic decays in the charm sector have been well studied in recent years. With the largest data sample near $D\bar D$ threshold, precision measurements of leptonic and semileptonic decays of charm meson and baryon are perfromed at BESIII. Test for letpon flavor universality is also performed. Sensitivity for rare leptonic and semileptonic charm decays is significantly improved taking advantage of the huge statistics in LHCb and the $B$ factories.
Although the Standard Model has been firmly established, the search for physics beyond the SM is ongoing by investigating new experimental probes. Rare charm decays are a unique tool to access New Physics studies. The high luminosity achieved by the modern experiments and their high precision allow for rare charm decay studies in different scenarios. In this work, some of the most recent experimental results will be discussed in detail.
Recent experimental bounds on rare charm decays offer a chance to improve our theoretical understanding of physics present in $c \to u γ$ and $c \to u l^+ l^-$ transitions. Standard Model and New Physics contributions are reviewed for inclusive and exclusive $D \to Vγ$, $D^+ \to π^+ l^+ l^-$, $D \to l^+ l^-$ decays. Observables important for search of New Physics are discussed. Possibility to observe CP violation in rare charm decays is questioned.
We study the effects of models with a warped extra dimension on rare charm decays. While the new degrees of freedom in these models are bounded above a few TeV, they can leave signatures in rare charm decays with their tiny Standard Model background. We look at several channels with leptons in the final state along with several asymmetries of both kinematical and dynamical nature. CPT invariance is `usable' for analyzing the impacts of new dynamics in $D$ meson decays and in particular, rare decays of charm mesons.
Semileptonic Flavor Changing Neutral Current decays of charmed hadrons uniquely probe the up-sector of the Standard Model. Clean null test observables, such as CP-asymmetries, lepton-universality ratios, missing energy modes, lepton flavor violating modes and angular observables can be studied in a variety of charmed meson and baryon modes. An overview of null test opportunities with rare charm decays is presented and similarities and complementarities of different modes are worked out.
