Exploiting 
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 asymmetries in rare charm decays

Bause, Rigo; Gisbert, Hector; Golz, Marcel; Hiller, Gudrun

doi:10.1103/physrevd.101.115006

“…refs. [4][5][6][9][10][11][12][13], which focused on defining observables and determining the possible effects of BSM physics both model-independent and for specific BSM physics scenarios.…”

Section: Jhep04(2021)158mentioning

confidence: 99%

Disentangling QCD and new physics in D → πℓ+ℓ−

Bharucha

¹

,

Boito

²

,

Meaux

³

2021

J. High Energ. Phys.

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In this paper we consider the decay D+ → π+ℓ+ℓ−, addressing in particular the resonance contributions as well as the relatively large contributions from the weak annihilation diagrams. For the weak annihilation diagrams we include known results from QCD factorisation at low q2 and at high q2, adapting the existing calculation for B decays in the Operator Product Expansion. The hadronic resonance contributions are obtained through a dispersion relation, modelling the spectral functions as towers of Regge-like resonances in each channel, as suggested by Shifman, imposing the partonic behaviour in the deep Euclidean. The parameters of the model are extracted using e+e− → (hadrons) and τ → (hadrons) + ντ data as well as the branching ratios for the resonant decays D+ → π+R(R → ℓ+ℓ−), with R = ρ, ω, and ϕ. We perform a thorough error analysis, and present our results for the Standard Model differential branching ratio as a function of q2. Focusing then on the observables FH and AFB, we consider the sensitivity of this channel to effects of physics beyond the Standard Model, both in a model independent way and for the case of leptoquarks.

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“…is consistent with zero, would be an indication of physics beyond the SM [7][8][9][10]. Here, τ D + and τ D 0 represent the D + and D 0 lifetimes and B +− , B 00 and B +0 represent the branching fractions of D 0 → π + π − , D 0 → π 0 π 0 and D + → π + π 0 decays, respectively.…”

Section: Introductionmentioning

confidence: 99%

“…The SCS modes D + s → K + π 0 , D + → π + η and D + s → K + η receive contributions from two different weak phases, proportional to the products of the CKM matrix elements V cd V * ud and V cs V * us , allowing CP violation at tree-level. In the Standard Model (SM), the CP asymmetries are expected to be of the order 10 −4 -10 −3 [2][3][4][5][6][7]. The CF mode D + s → π + η and the DCS modes D + → K + π 0 and D + → K + η receive contributions from only one weak phase at tree-level.…”

Section: Introductionmentioning

confidence: 99%

Search for CP violation in $$ {D}_{(s)}^{+}\to {h}^{+}{\pi}^0 $$ and $$ {D}_{(s)}^{+}\to {h}^{+}\eta $$ decays

Aaij

¹

,

Beteta²,

Ackernley³

et al. 2021

J. High Energ. Phys.

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Searches for CP violation in the two-body decays $$ {D}_{(s)}^{+}\to {h}^{+}{\pi}^0 $$ D s + → h + π 0 and $$ {D}_{(s)}^{+}\to {h}^{+}\eta $$ D s + → h + η (where h+ denotes a π+ or K+ meson) are performed using pp collision data collected by the LHCb experiment corresponding to either 9 fb−1 or 6 fb−1 of integrated luminosity. The π0 and η mesons are reconstructed using the e+e−γ final state, which can proceed as three-body decays π0→ e+e−γ and η → e+e−γ, or via the two-body decays π0→ γγ and η → γγ followed by a photon conversion. The measurements are made relative to the control modes $$ {D}_{(s)}^{+}\to {K}_{\mathrm{S}}^0{h}^{+} $$ D s + → K S 0 h + to cancel the production and detection asymmetries. The CP asymmetries are measured to be$$ {\displaystyle \begin{array}{c}{\mathcal{A}}_{CP}\left({D}^{+}\to {\pi}^{+}{\pi}^0\right)=\left(-1.3\pm 0.9\pm 0.6\right)\%,\\ {}{\mathcal{A}}_{CP}\left({D}^{+}\to {K}^{+}{\pi}^0\right)=\left(-3.2\pm 4.7\pm 2.1\right)\%,\\ {}\begin{array}{c}{\mathcal{A}}_{CP}\left({D}^{+}\to {\pi}^{+}\eta \right)=\left(-0.2\pm 0.8\pm 0.4\right)\%,\\ {}{\mathcal{A}}_{CP}\left({D}^{+}\to {K}^{+}\eta \right)=\left(-6\pm 10\pm 4\right)\%,\\ {}\begin{array}{c}{\mathcal{A}}_{CP}\left({D}_s^{+}\to {K}^{+}{\pi}^0\right)=\left(-0.8\pm 3.9\pm 1.2\right)\%,\\ {}\begin{array}{c}{\mathcal{A}}_{CP}\left({D}_s^{+}\to {\pi}^{+}\eta \right)=\left(0.8\pm 0.7\pm 0.5\right)\%,\\ {}{\mathcal{A}}_{CP}\left({D}_s^{+}\to {K}^{+}\eta \right)=\left(0.9\pm 3.7\pm 1.1\right)\%,\end{array}\end{array}\end{array}\end{array}} $$ A CP D + → π + π 0 = − 1.3 ± 0.9 ± 0.6 % , A CP D + → K + π 0 = − 3.2 ± 4.7 ± 2.1 % , A CP D + → π + η = − 0.2 ± 0.8 ± 0.4 % , A CP D + → K + η = − 6 ± 10 ± 4 % , A CP D s + → K + π 0 = − 0.8 ± 3.9 ± 1.2 % , A CP D s + → π + η = 0.8 ± 0.7 ± 0.5 % , A CP D s + → K + η = 0.9 ± 3.7 ± 1.1 % , where the first uncertainties are statistical and the second systematic. These results are consistent with no CP violation and mostly constitute the most precise measurements of $$ {\mathcal{A}}_{CP} $$ A CP in these decay modes to date.

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“…The potential of c → u + − processes to constrain new physics has been discussed in the literature [8][9][10][11]. Model-independent constraints on Wilson coefficients in effective field theory have been considered, as have specific classes of models.…”

Section: Introductionmentioning

confidence: 99%

Searches for 25 rare and forbidden decays of D+ and $$ {D}_s^{+} $$ mesons

Aaij

¹

,

Beteta²,

Ackernley³

et al. 2021

J. High Energ. Phys.

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A search is performed for rare and forbidden charm decays of the form $$ {D}_{(s)}^{+}\to {h}^{\pm }{\mathrm{\ell}}^{+}{\mathrm{\ell}}^{\left(\prime \right)\mp } $$ D s + → h ± ℓ + ℓ ′ ∓ , where h± is a pion or kaon and ℓ(′)± is an electron or muon. The measurements are performed using proton-proton collision data, corresponding to an integrated luminosity of 1.6 fb−1, collected by the LHCb experiment in 2016. No evidence is observed for the 25 decay modes that are investigated and 90 % confidence level limits on the branching fractions are set between 1.4 × 10−8 and 6.4 × 10−6. In most cases, these results represent an improvement on existing limits by one to two orders of magnitude.

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Exploiting CP asymmetries in rare charm decays

Cited by 39 publications

References 37 publications

Disentangling QCD and new physics in D → πℓ+ℓ−

Disentangling QCD and new physics in D → πℓ+ℓ−

Search for CP violation in $$ {D}_{(s)}^{+}\to {h}^{+}{\pi}^0 $$ and $$ {D}_{(s)}^{+}\to {h}^{+}\eta $$ decays

Searches for 25 rare and forbidden decays of D+ and $$ {D}_s^{+} $$ mesons

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