New-physics signatures via CP violation in η(′) → π0μ+μ− and η′ → ημ+μ− decays (original) (raw)
Related papers
2024
A complete theoretical analysis of the-conserving semileptonic decays () → 0 + − and → + − (= or) is carried out within the framework of the Vector Meson Dominance (VMD) model. An existing phenomenological model is used to parametrise the VMD coupling constants and the associated numerical values are obtained from an optimisation fit to → and → radiative decays (= 0 , , and = 0 , ,). Theoretical predictions for the six decay widths and associated dilepton energy spectra are calculated and presented. In addition, we investigate the prospect of observing new-physics signatures via violation in () → 0 + − and → + − decays at the REDTOP experiment. We make use of the SMEFT to parametrise the new-physics-violating effects and find that the projected REDTOP statistics are not competitive with respect to nEDM experiments for these particular processes.
Search for the CP-violating strong decays η→π+π− and η′(958)→π+π−
Physics Letters B, 2017
A search for the CP-violating strong decays η → π + π − and η (958) → π + π − has been performed using approximately 2.5 × 10 7 events of each of the decays D + → π + π + π − and D + s → π + π + π − , recorded by the LHCb experiment. The data set corresponds to an integrated luminosity of 3.0 fb −1 of pp collision data recorded during LHC Run 1 and 0.3 fb −1 recorded in Run 2. No evidence is seen for D + (s) → π + η () with η () → π + π − , and upper limits at 90% confidence level are set on the branching fractions, B(η → π + π −) < 1.6×10 −5 and B(η → π + π −) < 1.8×10 −5. The limit for the η decay is comparable with the existing one, while that for the η is a factor of three smaller than the previous limit.
Observation of D^{+}→K^{+}η^{(}′^{)} and Search for CP Violation in D^{+}→π^{+}η^{(}′^{)} Decays
Physical Review Letters, 2011
We report the first observation of the doubly Cabibbo-suppressed decays D + → K + η (′) using a 791 fb −1 data sample collected with the Belle detector at the KEKB asymmetric-energy e + e − collider. The ratio of the branching fractions of doubly Cabibbo-suppressed relative to singly Cabibbosuppressed D + → π + η (′) decays are B(D + → K + η)/B(D + → π + η) = (3.06 ± 0.43 ± 0.14)% and B(D + → K + η ′)/B(D + → π + η ′) = (3.77 ± 0.39 ± 0.10)%. From these, we find that the relative final-state phase difference between the tree and annihilation amplitudes in D + decays, δT A, is (72 ± 9) • or (288 ± 9) •. We also report the most precise measurements of CP asymmetries to date: A D + →π + η CP = (+1.74 ± 1.13 ± 0.19)% and A D + →π + η ′ CP = (−0.12 ± 1.12 ± 0.17)%.
IOP Conf. Series: Journal of Physics, 2017
REDTOP is a novel experiment proposed at the Delivery Ring of Fermilab with the intent of producing more than 10 13 η mesons per year to detect possible rare η decays which can be a clear evidence of the existence of Physics Beyond the Standard Model. Such statistics are sufficient for investigating several discrete symmetry violations, searching for new particles and interactions and to perform precision studies. One of the golden processes to study is the η → π + π − π 0 decay [7], where π 0 decays promptly into two photons. In the context of the Standard Model, the dynamics of the charged pions is symmetric in this process. Thus, any mirror asymmetry in the Dalitz plot would be a direct indication of C and CP violation. We present a study on the performance of the REDTOP experiment detector by reconstructing the invariant mass of the final state π + π − γγ using Monte Carlo samples.
Observation of η′ Decays to π+π-π0 and π+π-e+e
Physical Review Letters, 2009
Using ψ(2S)→π + π − J/ψ, J/ψ → γη ′ events acquired with the CLEO-c detector at the CESR e + e − collider, we make the first observations of the decays η ′ → π + π − π 0 and η ′ → π + π − e + e − , measuring absolute branching fractions (37 +11 − 9 ± 4) × 10 −4 and (25 +12 − 9 ± 5) × 10 −4 , respectively. For η ′ → π + π − π 0 , this result probes the mechanism of isospin violation and the roles of π 0 /η/η ′mixing and final state rescattering in strong decays. We also set upper limits on branching fractions for η ′ decays to π + π − µ + µ − , 2(π + π −), π + π − 2π 0 , 2(π + π −)π 0 , 3(π + π −), and invisible final states.
Search for direct CP-violation in decays
Physics Letters B, 2006
A search for direct CP-violation in K ± → π ± π 0 π 0 decay based on 47.14 million events has been performed by the NA48/2 experiment at the CERN SPS. The asymmetry in the Dalitz plot linear slopes A g = (g + − g − ) / (g + + g − ) is measured to be A g = (1.8±2.6)·10 −4 . The design of the experiment and the method of analysis provide good control of instrumental charge asymmetries in this measurement. The precision of the result is limited by statistics and is almost one order of magnitude better than that of previous measurements by other experiments.
2007
We present a measurement of the ratio of the decay rates Γ(K L → π + π −)/Γ(K L → π ± e ∓ ν), denoted as Γ K2π /Γ Ke3. The analysis is based on data taken during a dedicated run in 1999 by the NA48 experiment at the CERN SPS. Using a sample of 47000 K 2π and five million K e3 decays, we find Γ K2π /Γ Ke3 = (4.835 ± 0.022 stat. ± 0.016 syst.) × 10 −3. From this we derive the branching ratio of the CP violating decay K L → π + π − and the CP violation parameter |η +− |. Excluding the CP conserving direct photon emission component K L → π + π − γ, we obtain the results BR(K L → π + π −) = (1.941 ± 0.019) × 10 −3 and |η +− | = (2.223 ± 0.012) × 10 −3 .
Search for CP violation in the decay tau(-) -> pi K--(s)0 (>= 0 pi(0))v(tau)
Physical Review D, 2012
ABSTRACT We report a search for CPCPCP violation in the decay ensuremathtauensuremath−ensuremathrightarrowensuremathpiensuremath−KS0(ensuremathge0ensuremathpi0)ensuremathnuensuremathtau{\ensuremath{\tau}}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}{K}_{S}^{0}(\ensuremath{\ge}0{\ensuremath{\pi}}^{0}){\ensuremath{\nu}}_{\ensuremath{\tau}}ensuremathtauensuremath−ensuremathrightarrowensuremathpiensuremath−KS0(ensuremathge0ensuremathpi0)ensuremathnuensuremathtau using a data set of 437ifmmodetimeselsetexttimesfi106437\ifmmode\times\else\texttimes\fi{}{10}^{6}437ifmmodetimeselsetexttimesfi106 ensuremathtau\ensuremath{\tau}ensuremathtau-lepton pairs, corresponding to an integrated luminosity of 476texttextmathrmfbensuremath−1476\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}476texttextmathrmfbensuremath−1, collected with the BABAR detector at the PEP-II asymmetric-energy e+eensuremath−{e}^{+}{e}^{\ensuremath{-}}e+eensuremath− storage rings. The CPCPCP-violating decay-rate asymmetry is determined to be (ensuremath−0.36ifmmodepmelsetextpmfi0.23ifmmodepmelsetextpmfi0.11)(\ensuremath{-}0.36\ifmmode\pm\else\textpm\fi{}0.23\ifmmode\pm\else\textpm\fi{}0.11)%(ensuremath−0.36ifmmodepmelsetextpmfi0.23ifmmodepmelsetextpmfi0.11) approximately 2.8 standard deviations from the standard model prediction of (0.36ifmmodepmelsetextpmfi0.01)(0.36\ifmmode\pm\else\textpm\fi{}0.01)%(0.36ifmmodepmelsetextpmfi0.01).