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Kumar, M.

Publications and source records attributed to Kumar, M..

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

First measurement of the \( {\Lambda}_c^{+} \) → pη ' decay

We present the first measurement of the branching fraction of the singly Cabibbo-suppressed (SCS) decay \( {\Lambda}_c^{+} \) → pη ' with η ' → ηπ + π – , using a data sample corresponding to an integrated luminosity of 981 fb – 1 , collected by the Belle detector at the KEKB e + e – asymmetric-energy collider. A significant \( {\Lambda}_c^{+} \) → pη ' signal is observed for the first time with a signal significance of 5.4 σ . The relative branching fraction with respect to the normalization mode \( {\Lambda}_c^{+} \) → pK – π + is measured to be $$ \frac{\mathcal{B}\left({\Lambda}_c^{+}\to p\eta^{\prime}\right)}{\mathcal{B}\left({\Lambda}_c^{+}\to {pK}^{-}{\pi}^{+}\right)}=\left(7.54\pm 1.32\pm 0.73\right)\times {10}^{-3}, $$ where the uncertainties are statistical and systematic, respectively. Using the world-average value of \( \mathcal{B}\left({\Lambda}_c^{+}\to {pK}^{-}{\pi}^{+}\right) \) = (6 . 28 ± 0 . 32) × 10 – 2 , we obtain $$ \mathcal{B}\left({\Lambda}_c^{+}\to p\eta^{\prime}\right)=\left(4.73\pm 0.82\pm 0.46\pm 0.24\right)\times {10}^{-4}, $$ where the uncertainties are statistical, systematic, and from \( \mathcal{B}\left({\Lambda}_c^{+}\to {pK}^{-}{\pi}^{+}\right) \) , respectively.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

An experiment for electron-hadron scattering at the LHC

Abstract Novel considerations are presented on the physics, apparatus and accelerator designs for a future, luminous, energy frontier electron-hadron ( eh ) scattering experiment at the LHC in the thirties for which key physics topics and their relation to the hadron-hadron HL-LHC physics programme are discussed. Demands are derived set by these physics topics on the design of the LHeC detector, a corresponding update of which is described. Optimisations on the accelerator design, especially the interaction region (IR), are presented. Initial accelerator considerations indicate that a common IR is possible to be built which alternately could serve eh and hh collisions while other experiments would stay on hh in either condition. A forward-backward symmetrised option of the LHeC detector is sketched which would permit extending the LHeC physics programme to also include aspects of hadron-hadron physics. The vision of a joint eh and hh physics experiment is shown to open new prospects for solving fundamental problems of high energy heavy-ion physics including the partonic structure of nuclei and the emergence of hydrodynamics in quantum field theory while the genuine TeV scale DIS physics is of unprecedented rank.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Search for lepton-flavor-violating tau-lepton decays to ℓγ at Belle

Charged lepton flavor violation is forbidden in the Standard Model but possible in several new physics scenarios. In many of these models, the radiative decays τ ± → ℓ ± γ (ℓ = e, μ) are predicted to have a sizeable probability, making them particularly interesting channels to search at various experiments. An updated search via τ ± → ℓ ± γ using full data of the Belle experiment, corresponding to an integrated luminosity of 988 fb –1 , is reported for charged lepton flavor violation. No significant excess over background predictions from the Standard Model is observed, and the upper limits on the branching fractions, B(τ ± → μ ± γ) ≤ 4.2 × 10 –8 and B(τ ± → e ± γ) ≤ 5.6 × 10 –8 , are set at 90% confidence level.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

Measurement of branching fractions and search for CP violation in $D^0 → π^+π^-η, D^0 → K^+K^-η$, and $D^0 → Φη$ at Belle

We measure the branching fractions and CP asymmetries for the singly Cabibbo-suppressed decays $D^0 → π^+π^-η, D^0 → K^+K^-η$, and $D^0 → Φη$, using 980 fb -1 of data from the Belle experiment at the KEKB e + e - collider. We obtain $$\mathcal{B}(D^0 → π^+π^-η = \mathrm{[1.22 ± 0.02 (stat) ± 0.02(syst) ± 0.03}(\mathcal{B}_{\mathrm{ref}})] \mathrm{x 10^{-3}}$$ $$\mathcal{B}(D^0 → K^+K^-η = \mathrm{[1.80^{+0.07}_{-0.06}(stat) ± 0.04 (syst) ± 0.05}(\mathcal{B}_{\mathrm{ref}})] \mathrm{x 10^{-4}}$$ $$\mathcal{B}(D^0 → Φη = \mathrm{[1.84 ± 0.09 (stat) ± 0.0 (syst) ± 0.05}(\mathcal{B}_{\mathrm{ref}})] \mathrm{x 10^{-4}}$$ where the third uncertainty ($\mathcal{B}_{\mathrm{ref}}$) is from the uncertainty in the branching fraction of the reference mode $D^0 → K^-π^+η$. The color-suppressed decay $D^0 → Φη$ is observed for the first time, with very high significance. The results for the CP asymmetries are $$A_{CP} (D^0 → π^+π^-η) = \mathrm{[0.9 ± 1.2 (stat) ± 0.5 (syst)]}\%$$ $$A_{CP} (D^0 → K^+K^-η) = \mathrm{[-1.4 ± 3.3 (stat) ± 1.1 (syst)]}\%$$ $$A_{CP} (D^0 → Φη) = \mathrm{[-1.9 ± 4.4 (stat) ± 0.6 (syst)]}\%$$ The results for $D^0 → π^+π^-η$ are a significant improvement over previous results. The branching fraction and A CP results for $D^0 → K^+K^-η$, and the ACP result for $D^0 → Φη$, are the first such measurements. No evidence for CP violation is found in any of these decays.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

Search for the dark photon in B 0 → A'A', A' → e + e – , μ + μ – , and π + π – decays at Belle

We present a search for the dark photon A' in the B 0 → A'A' decays, where A' subsequently decays to e + e – , μ + μ – , and π + π – . The search is performed by analyzing 772 × 10 6 $B$$\overline{B}$ events collected by the Belle detector at the KEKB e + e – energy-asymmetric collider at the Υ(4S) resonance. No signal is found in the dark photon mass range 0.01 GeV/c 2 ≤ m A' ≤ 2.62 GeV/c 2 , and we set upper limits of the branching fraction of B0 → A'A' at the 90% confidence level. The products of branching fractions, B(B 0 →A'A')×B(A'→e + e – ) 2 and B(B 0 →A'A')×B(A'→μ + μ – ) 2 , have limits of the order of 10 –8 depending on the A' mass. Furthermore, considering A' decay rate to each pair of charged particles, the upper limits of B(B 0 →A'A') are of the order of 10 –8 –10 –5 . From the upper limits of B(B 0 →A'A'), we obtain the Higgs portal coupling for each assumed dark photon and dark Higgs mass. The Higgs portal couplings are of the order of 10 –2 –10 –1 at m h' ≃m B 0 ± 40 MeV/c 2 and 10 –1 –1 at m h' ≃m B 0 ± 3 GeV/c 2 .

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗