Lepton universality and lepton flavor conservation tests with dineutrino modes

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

doi:10.48550/arxiv.2007.05001

Cited by 8 publications

(39 citation statements)

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“…Operators with charged lepton singlets E, such as Qγ µ Q Ēγ µ E are not connected to the dineutrino processes. Note, in weak effective theory they break the relation C 9 = −C 10 , see the discussion after (7). By construction, all Wilson coefficients in SMEFT are induced by BSM physics.…”

Section: B Standard Model Effective Field Theorymentioning

confidence: 94%

“…Importantly, the flavor of neutrinos is experimentally untagged, therefore a measurement of a dineutrino branching ratio involves an incoherent sum of neutrino flavors i, j = e, µ, τ , B(q → q ν ν) = i,j B(q → q ν i νj ). This way, the dineutrino modes automatically include contributions from lepton universality violation, or lepton flavor violation, allowing for tests thereof [7].…”

Section: Introductionmentioning

confidence: 99%

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Interplay of dineutrino modes with semileptonic rare $\boldsymbol{B}$-decays

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Gisbert,

Golz

et al. 2021

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We present a systematic global analysis of dineutrino modes b → q ν ν, q = d, s, and charged dilepton b → q + − transitions. We derive improved or even entirely new limits on dineutrino branching ratios including decays B 0 → (K 0 , Xs) ν ν, Bs → φ ν ν and B 0 → (π 0 , ρ 0 ) ν ν from dineutrino modes which presently are best constrained: B + → (K + , π + , ρ + ) ν ν and B 0 → K * 0 ν ν. Using SMEFT we obtain new flavor constraints from the dineutrino modes, which are stronger than the corresponding ones from charged dilepton rare b-decay or Drell-Yan data, for eτ and τ τ final states, as well as for µτ ones in b → s processes. The method also allows to put novel constraints on semileptonic four-fermion operators with top quarks. Implications for ditau modes b → s τ + τ − and b → d τ + τ − are worked out. Even stronger constraints are obtained in simplified BSM frameworks such as leptoquarks and Z -models. Furthermore, the interplay between dineutrinos and charged dileptons allows for concrete, novel tests of lepton universality in rare B-decays. Performing a global fit to b → s µ + µ − , sγ transitions we find that lepton universality predicts the ratio of the B 0 → K * 0 ν ν to B 0 → K 0 ν ν (B + → K + ν ν) branching fractions to be within 1.7 to 2.6 (1.6 to 2.4) at 1 σ, a region that includes the standard model, and that can be narrowed with improved charged dilepton data. There is sizable room outside this region where universality is broken and that can be probed with the Belle II experiment. Using results of a fit to B 0 → µ + µ − , B 0 s → K * 0 µ + µ − and B + → π + µ + µ − data we obtain an analogous relation for |∆b| = |∆d| = 1 transitions: if lepton universality holds the ratio of the B 0 → ρ 0 ν ν to B 0 → π 0 ν ν (B + → π + ν ν) branching fractions is within 2.5 to 5.7 (1.2 to 2.6) at 1 σ. Putting upper limits on B(Bs → ν ν) at the level of 10 −5 and B(B 0 → ν ν) below 10 −6 would allow to control backgrounds from (pseudo-)scalar operators such as those induced by light right-handed neutrinos.

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Section: B Standard Model Effective Field Theorymentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

Interplay of dineutrino modes with semileptonic rare $\boldsymbol{B}$-decays

Bause,

Gisbert,

Golz

et al. 2021

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“…where 𝑁 = 𝑈 (𝑁 = 𝐷) represents the up-quark sector (down-quark sector), and 𝐴 = 𝐿(𝑅) denotes left-(right-) handed quark currents. Interestingly, 𝐶 𝑁 𝑅 = 𝐾 𝑁 𝑅 holds model-independently, while 𝐶 𝑁 𝐿 is not fixed by 𝐾 𝑁 𝐿 in general due to the different relative signs of 𝐶 (1) ℓ𝑞 and 𝐶 (3) ℓ𝑞 . Expressing Eqs.…”

Section: 𝑺𝑼(2) 𝑳 -Link Between Dineutrino and Charged Dilepton Couplingsmentioning

confidence: 99%

“…where 𝑊 is the Pontecorvo-Maki-Nakagawa-Sakata (PMNS) matrix and 𝜆 ∼ 0.2 the Wolfenstein parameter, and summing lepton flavors 𝑖, 𝑗 incoherently, one obtains the following identity [1] ∑︁…”

Section: 𝑺𝑼(2) 𝑳 -Link Between Dineutrino and Charged Dilepton Couplingsmentioning

confidence: 99%

“…In addition, its environment is enriched with further tests if leptons are involved, that is 𝑞 𝛼 𝑞 𝛽 ℓ + 𝑖 ℓ − 𝑗 and 𝑞 𝛼 𝑞 𝛽 ν𝑖 𝜈 𝑗 . We exploit the 𝑆𝑈 (2) 𝐿 -link between left-handed charged lepton and neutrino couplings, which may be used to assess charged lepton flavor conservation (cLFC) and lepton universality (LU) quantitatively using flavor-summed dineutrino observables [1]. This link (3) is presented for |Δ 𝑞 𝛼 | = |Δ 𝑞 𝛽 | = 1 processes, but we stress that it holds analogously for other conserved quark transitions, both in the up-and down-sector.…”

Section: Introductionmentioning

confidence: 99%

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Dineutrino modes probing lepton flavor violation

Bause¹,

Gisbert²,

Golz³

et al. 2021

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𝑆𝑈 (2) 𝐿 -invariance links charged dilepton q 𝑞 ℓ + ℓ − and dineutrino q 𝑞 ν 𝜈 couplings. This connection can be established using the Standard Model Effective Field Theory framework, and allows to perform complementary experimental tests of lepton universality and charged lepton flavor conservation with flavor-summed dineutrino observables. We present its phenomenological implications for the branching ratios of rare charm decays 𝑐 → 𝑢 𝜈 ν and rare 𝐵 decays 𝑏 → 𝑠 ν 𝜈 decays.

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Rare charm c→uνν¯ dineutrino null tests for e+
Bause
¹
,
Gisbert
²
,
Golz
³

et al. 2021
Phys. Rev. D
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36
2
84
0
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Rare |∆c| = |∆u| = 1 transitions into dineutrinos are strongly GIM-suppressed and constitute excellent null tests of the standard model. While branching ratios of D → P ν ν, D → P + P − ν ν, P = π, K, baryonic Λ + c → p ν ν, and Ξ + c → Σ + ν ν and inclusive D → Xν ν decays are experimentally unconstrained, signals of new physics can be just around the corner. We provide model-independent upper limits on branching ratios reaching few ×10 −5 in the most general case of arbitrary lepton flavor structure, ∼ 10 −5 for scenarios with charged lepton conservation and few ×10 −6 assuming lepton universality. We also give upper limits in Z and leptoquark models. The presence of light right-handed neutrinos can affect these limits, a possibility that can occur for lepton number violation at a TeV, and that can be excluded with an improved bound on B(D 0 → invisibles) at the level of ∼ 10 −6 , about two orders of magnitude better than the present one. Signatures of c → uν ν modes contain missing energy and are suited for experimental searches at e + e − -facilities, such as BES III, Belle II and future e + e − -colliders, such as the FCC-ee running at the Z.

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Lepton universality and lepton flavor conservation tests with dineutrino modes

Cited by 8 publications

References 0 publications

Interplay of dineutrino modes with semileptonic rare $\boldsymbol{B}$-decays

Interplay of dineutrino modes with semileptonic rare $\boldsymbol{B}$-decays

Dineutrino modes probing lepton flavor violation

Rare charm c→uνν¯ dineutrino null tests for e+
Bause
¹
,
Gisbert
²
,
Golz
³

et al. 2021
Phys. Rev. D
Self Cite
36
2
84
0
View full text Add to dashboard Cite

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Lepton universality and lepton flavor conservation tests with dineutrino modes

Cited by 8 publications

References 0 publications

Interplay of dineutrino modes with semileptonic rare $\boldsymbol{B}$-decays

Interplay of dineutrino modes with semileptonic rare $\boldsymbol{B}$-decays

Dineutrino modes probing lepton flavor violation

Rare charm c→uνν¯ dineutrino null tests for e+Bause1, Gisbert2, Golz3 et al. 2021Phys. Rev. DSelf Cite362840View full textAdd to dashboardCite

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About

Rare charm c→uνν¯ dineutrino null tests for e+
Bause
¹
,
Gisbert
²
,
Golz
³

et al. 2021
Phys. Rev. D
Self Cite
36
2
84
0
View full text Add to dashboard Cite