arXiv subjects

P. Behera

Publications and source records attributed to P. Behera.

At least 127 records · Page 7Linked to original sources

arXiv2020

First search for the $η_{c2}(1D)$ in $B$ decays at Belle

The first dedicated search for the $η_{c2}(1D)$ is carried out using the decays $B^+ \rightarrow η_{c2}(1D) K^+$, $B^0 \rightarrow η_{c2}(1D) K^0_S$, $B^0 \rightarrow η_{c2}(1D) π^- K^+$, and $B^+ \rightarrow η_{c2}(1D) π^+ K^0_S$ with $η_{c2}(1D) \to h_c γ$. No significant signal is found. For the $η_{c2}(1D)$ mass range between $3795$ and $3845\ \mathrm{MeV}/c^2$, the branching-fraction upper limits are determined to be $\mathcal{B}(B^+ \rightarrow η_{c2}(1D) K^+) \times \mathcal{B}(η_{c2}(1D) \to h_c γ) < 3.7 \times 10^{-5}$, $\mathcal{B}(B^0 \rightarrow η_{c2}(1D) K^0_S) \times \mathcal{B}(η_{c2}(1D) \to h_c γ) < 3.5 \times 10^{-5}$, $\mathcal{B}(B^0 \rightarrow η_{c2}(1D) π^- K^+) \times \mathcal{B}(η_{c2}(1D) \to h_c γ) < 1.0 \times 10^{-4}$, and $\mathcal{B}(B^+ \rightarrow η_{c2}(1D) π^+ K^0_S) \times \mathcal{B}(η_{c2}(1D) \to h_c γ) < 1.1 \times 10^{-4}$ at 90% C. L. The analysis is based on the 711 $\mathrm{fb}^{-1}$ data sample collected on the $Υ(4S)$ resonance by the Belle detector, which operated at the KEKB asymmetric-energy $e^+ e^-$ collider.

hep-ex↗

arXiv2020

Evidence for a vector charmonium-like state in $e^+e^- \to D^+_sD^*_{s2}(2573)^-+c.c.$

We report the measurement of $e^+e^- \to D^+_sD^*_{s2}(2573)^-+c.c.$ via initial-state radiation using a data sample of an integrated luminosity of 921.9 fb$^{-1}$ collected with the Belle detector at the $Υ(4S)$ and nearby. We find evidence for an enhancement with a 3.4$σ$ significance in the invariant mass of $D^+_sD^*_{s2}(2573)^- +c.c.$ The measured mass and width are $(4619.8^{+8.9}_{-8.0}({\rm stat.})\pm2.3({\rm syst.}))~{\rm MeV}/c^{2}$ and $(47.0^{+31.3}_{-14.8}({\rm stat.})\pm4.6({\rm syst.}))~{\rm MeV}$, respectively. The mass, width, and quantum numbers of this enhancement are consistent with the charmonium-like state at 4626 MeV/$c^2$ recently reported by Belle in $e^+e^-\to D^+_sD_{s1}(2536)^-+c.c.$ The product of the $e^+e^-\to D^+_sD^*_{s2}(2573)^-+c.c.$ cross section and the branching fraction of $D^*_{s2}(2573)^-\to{\bar D}^0K^-$ is measured from $D^+_sD^*_{s2}(2573)^-$ threshold to 5.6 GeV.

hep-ex↗

arXiv2020

Update of inclusive cross sections of single and pairs of identified light charged hadrons

We report new measurements of the production cross sections of pairs of charged pions and kaons as a function of their fractional energies using various fractional-energy definitions. Two different fractional-energy definitions were used and compared to the conventional fractional-energy definition reported previously. The new variables aim at either identifying dihadron cross sections in terms of single-hadron fragmentation functions, or to provide a means of characterizing the transverse momentum created in the fragmentation process. The results were obtained applying the updated initial-state radiation correction used in other recent Belle publications on light-hadron production cross sections. In addition, production cross sections of single charged pions, kaons, and protons were also updated using this initial-state radiation correction. The cross sections are obtained from a $558\,{\rm fb}^{-1}$ data sample collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider.

hep-ex↗

arXiv2019

Measurements of the Branching Fractions ${\cal B}(B^{-} \to \barΛ_{c}^{-} Ξ_{c}^{'0})$, ${\cal B}(B^{-} \to \barΛ_{c}^{-} Ξ_{c}(2645)^{0})$ and ${\cal B}(B^{-} \to \barΛ_{c}^{-} Ξ_{c}(2790)^{0}) $

Using the data sample of 711 fb$^{-1}$ of $Υ(4S)$ on-resonance data taken by the Belle detector at the KEKB asymmetric-energy electron-positron collider, we present the first measurements of branching fractions of the decays $B^{-} \to \barΛ_{c}^{-} Ξ_{c}^{'0}$, $B^{-} \to \barΛ_{c}^{-} Ξ_{c}(2645)^{0}$, and $B^{-} \to \barΛ_{c}^{-} Ξ_{c}(2790)^{0} $. The signal yields for these decays are extracted from the recoil mass spectrum of the system recoiling against $\barΛ_{c}^{-}$ baryons in selected $B^-$ candidates. The branching fraction of $B^{-} \to \barΛ_{c}^{-} Ξ_{c}(2790)^{0}$ is measured to be $ (1.1 \pm 0.4 \pm 0.2)\times 10^{-3}$, where the first uncertainty is statistical and the second systematic. The 90\% credibility level upper limits on ${\cal B}(B^{-} \to \barΛ_{c}^{-} Ξ_{c}^{'0})$ and ${\cal B}(B^{-} \to \barΛ_{c}^{-} Ξ_{c}(2645)^{0})$ are determined to be $6.5\times 10^{-4}$ and $7.9\times 10^{-4}$, respectively.

hep-ex↗

arXiv2019

Study of $B \to p {\bar p} ππ$

Using a data sample of $772 \times 10^6$ BB pairs collected on the $Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider, we report the observations of $B^0\to p{\bar p}π^+π^-$ and $B^+ \to p{\bar p}π^+π^0$. We measure a decay branching fraction of $(0.83 \pm 0.17 \pm 0.17) \times 10^-6$ in $B^0\to p{\bar p}π^+π^-$ for $M_{π^+π^-} < 1.22 GeV/c^2$ with a significance of 5.5 standard deviations. The contribution from $B0 \to p{\bar p}K^0$ is excluded. We measure a decay branching fraction of $(4.58 \pm 1.17 \pm 0.67) \times 10^-6$ for $B^+ \to p{\bar p}π^+π^0$ with $M_{π^+π^0} < 1.3 GeV/c^2$ with a significance of 5.4 standard deviations. We study the difference of the $M_{p{\bar p}}$ distributions in $B^0\to p{\bar p}π^+π^-$ and $B^+ \to p{\bar p}π^+π^0$.

hep-ex↗

arXiv2019

Search for $B^+ \to μ^+\, ν_μ$ and $B^+ \to μ^+\, N$ with inclusive tagging

We report the result for a search for the leptonic decay of $B^+ \to μ^+ \, ν_μ$ using the full Belle data set of 711 fb${}^{-1}$ of integrated luminosity at the $Υ(4S)$ resonance. In the Standard Model leptonic $B$-meson decays are helicity and CKM suppressed. To maximize sensitivity an inclusive tagging approach is used to reconstruct the second $B$ meson produced in the collision. The directional information from this second $B$ meson is used to boost the observed $μ$ into the signal $B$ meson rest-frame, in which the $μ$ has a monochromatic momentum spectrum. Though its momentum is smeared by the experimental resolution, this technique improves the analysis sensitivity considerably. Analyzing the $μ$ momentum spectrum in this frame we find $\mathcal{B}(B^+ \to μ^+ \, ν_μ) = \left( 5.3 \pm 2.0 \pm 0.9 \right) \times 10^{-7}$ with a one-sided significance of 2.8 standard deviations over the background-only hypothesis. This translates to a frequentist upper limit of $\mathcal{B}(B^+ \to μ^+ \, ν_μ) < 8.6 \times 10^{-7}$ at 90% CL. The experimental spectrum is then used to search for a massive sterile neutrino, $B^+ \to μ^+ \, N$, but no evidence is observed for a sterile neutrino with a mass in a range of 0 - 1.5 GeV. The determined $B^+ \to μ^+ \, ν_μ$ branching fraction limit is further used to constrain the mass and coupling space of the type II and type III two-Higgs-doublet models.

hep-ex↗

arXiv2019

Observation of a vector charmoniumlike state in $e^+e^- \to D^+_sD_{s1}(2536)^-+c.c.$

Using a data sample of 921.9 fb$^{-1}$ collected with the Belle detector, we study the process of $e^+e^-\to D^+_sD_{s1}(2536)^-+c.c.$ via initial-state radiation. We report the first observation of a vector charmoniumlike state decaying to $D^+_sD_{s1}(2536)^-+c.c.$ with a significance of 5.9$σ$, including the systematic uncertainties. The measured mass and width are $(4625.9^{+6.2}_{-6.0}({\rm stat.})\pm0.4({\rm syst.}))~{\rm MeV}/c^{2}$ and $(49.8^{+13.9}_{-11.5}({\rm stat.})\pm4.0({\rm syst.}))~{\rm MeV}$, respectively. The product of the $e^+e^-\to D^+_sD_{s1}(2536)^-+c.c.$ cross section and the branching fraction of $D_{s1}(2536)^-\to{\bar D}^{*0}K^-$ is measured from the $D_s \bar{D}_{s1}(2536)$ threshold to 5.59~GeV.

hep-ex↗

arXiv2019

Observation of the radiative decays of $Υ(1S)$ to $χ_{c1}$

We report the first observation of the radiative decay of the $Υ(1S)$ into a charmonium state. The statistical significance of the observed signal of $Υ(1S) \to γχ_{c1}$ is 6.3 standard deviations including systematics. The branching fraction is calculated to be Br($Υ(1S) \to γχ_{c1}$) = (4.7^{+2.4}_{-1.8} (stat) ^{+0.4}_{-0.5} (sys)) * 10^{-5}. We also searched for $Υ(1S)$ radiative decays into $χ_{c0,2}$ and $η_c(1S,2S)$ and set upper limits on their branching fractions. These results are obtained from a 24.9 fb^{-1} data sample collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider at a center-of-mass energy equal to the $Υ(2S)$ mass using $Υ(1S)$ tagging by the $Υ(2S) \to Υ(1S) π^+π^-$ transitions.

hep-ex↗

arXiv2019

Measurement of $\mathcal{R}(D)$ and $\mathcal{R}(D^*)$ with a semileptonic tagging method

The experimental results on the ratios of branching fractions $\mathcal{R}(D) = {\cal B}(\bar{B} \to D τ^- \barν_τ)/{\cal B}(\bar{B} \to D \ell^- \barν_{\ell})$ and $\mathcal{R}(D^*) = {\cal B}(\bar{B} \to D^* τ^- \barν_τ)/{\cal B}(\bar{B} \to D^* \ell^- \barν_{\ell})$, where $\ell$ denotes an electron or a muon, show a long-standing discrepancy with the Standard Model predictions, and might hint to a violation of lepton flavor universality. We report a new simultaneous measurement of $\mathcal{R}(D)$ and $\mathcal{R}(D^*)$, based on a data sample containing $772 \times 10^6$ $B\bar{B}$ events recorded at the $Υ(4S)$ resonance with the Belle detector at the KEKB $e^+ e^-$ collider. In this analysis the tag-side $B$ meson is reconstructed in a semileptonic decay mode and the signal-side $τ$ is reconstructed in a purely leptonic decay. The measured values are $\mathcal{R}(D)= 0.307 \pm 0.037 \pm 0.016$ and $\mathcal{R}(D^*) = 0.283 \pm 0.018 \pm 0.014$, where the first uncertainties are statistical and the second are systematic. These results are in agreement with the Standard Model predictions within $0.2$, $1.1$ and $0.8$ standard deviations for $\mathcal{R}(D)$, $\mathcal{R}(D^*)$ and their combination, respectively. This work constitutes the most precise measurements of $\mathcal{R}(D)$ and $\mathcal{R}(D^*)$ performed to date as well as the first result for $\mathcal{R}(D)$ based on a semileptonic tagging method.

hep-ex↗

arXiv2019

Observation of a new structure near 10.75 GeV in the energy dependence of the $e^+e^-\toΥ(nS)π^+π^-$ ($n=1,2,3$) cross sections

We report a new measurement of the $e^+e^-\toΥ(nS)π^+π^-$ ($n=1,2,3$) cross sections at energies from 10.52 to 11.02 GeV using data collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. We observe a new structure in the energy dependence of the cross sections; if described by a Breit-Wigner function its mass and width are found to be $M=(10752.7\pm5.9\,^{+0.7}_{-1.1})\,$MeV/$c^2$ and $Γ=(35.5^{+17.6}_{-11.3}\,^{+3.9}_{-3.3})\,$MeV, where the first error is statistical and the second is systematic. The global significance of the new structure including systematic uncertainty is 5.2 standard deviations. We also find evidence for the $e^+e^-\toΥ(1S)π^+π^-$ process at the energy 10.52 GeV, which is below the $B\bar{B}$ threshold.

hep-ex↗

arXiv2019

Observation of $ τ^- \rightarrow π^- ν_τ e^+ e^-$ and search for $τ^- \rightarrow π^- ν_τ μ^+ μ^-$

We present the first measurements of branching fractions of rare tau-lepton decays, $τ^- \rightarrow π^- ν_τ \ell^+ \ell^-$ ($\ell = e$ or $μ$), using a data sample corresponding to 562 fb$^{-1}$ collected at a center-of-mass energy of 10.58 GeV with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. The $τ^- \rightarrow π^- ν_τe^+ e^-$ decay is observed for the first time with 7.0$σ$ significance. The partial branching fraction determined by the structure-dependent mechanisms mediated by either a vector or an axial-vector current for the mass region $M_{πe e}>1.05$ GeV/$c^2$ is measured to be $\mathcal{B}(τ^-\rightarrow π^- ν_τe^+ e^-)[M_{π^- e^+ e^-}>1.05~{\rm GeV}/c^2] = (5.90 \pm 0.53 \pm 0.85 \pm 0.11) \times 10^{-6}$, where the first uncertainty is statistical, the second is systematic, and the third is due to the model dependence. In the full phase space, due to the different detection efficiencies for the structure-dependent mechanisms mediated by axial-vector and vector currents, the branching fraction varies from $\mathcal{B}_{A}(τ^-\rightarrow π^- ν_τe^+ e^-) = (1.46 \pm 0.13 \pm 0.21) \times 10^{-5}$ to $\mathcal{B}_{V}(τ^-\rightarrow π^- ν_τe^+ e^-) = (3.01 \pm 0.27 \pm 0.43) \times 10^{-5}$, respectively. An upper limit is set on the branching fraction of the $τ^- \rightarrow π^- ν_τμ^+ μ^-$ decay, $\mathcal{B}(τ^-\rightarrow π^- ν_τμ^+ μ^-) < 1.14 \times 10^{-5}$, at the 90% confidence level.

hep-ex↗

arXiv2019

Experimental determination of the isospin of $Λ_c(2765)^+/Σ_c(2765)^+$

We report an experimental determination of the isospin of $Λ_c(2765)^+/Σ_c(2765)^+$ using 980 fb$^{-1}$ data in the $e^+e^-$ annihilation around $\sqrt{s} = 10.6$ GeV collected by the Belle detector located at the KEKB collider. The isospin partners are searched for in the $Σ_c(2455)^{++/0} π^{0}$ channels, and no evidence was obtained. Thus the isospin is determined to be zero, and the particle is established to be a $Λ_c$.

hep-ex↗

arXiv2019

First measurements of absolute branching fractions of the $Ξ_c^+$ baryon at Belle

We present the first measurements of the absolute branching fractions of $Ξ_c^+$ decays into $Ξ^- π^+ π^+$ and $p K^- π^+$ final states. Our analysis is based on a data set of $(772\pm 11)\times 10^{6}$ $B\bar{B}$ pairs collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB $e^+e^-$ collider. We measure the absolute branching fraction of $\bar{B}^{0} \to \barΛ_{c}^{-} Ξ_{c}^{+}$ with the $Ξ_c^+$ recoiling against $\barΛ_c^-$ in $\bar{B}^0$ decays resulting in ${\cal B}(\bar{B}^{0} \to \barΛ_{c}^{-} Ξ_{c}^{+}) = [1.16 \pm 0.42(\rm stat.) \pm 0.15(\rm syst.)] \times 10^{-3}$. We then measure the product branching fractions ${\cal B}(\bar{B}^{0} \to \barΛ_c^- Ξ_c^+){\cal B}(Ξ_c^+ \to Ξ^- π^+ π^+)$ and ${\cal B}(\bar{B}^{0} \to \barΛ_c^- Ξ_c^+){\cal B}(Ξ_c^+ \to p K^- π^+)$. Dividing these product branching fractions by $\bar{B}^{0} \to \barΛ_{c}^{-} Ξ_{c}^{+}$ yields: ${\cal B}(Ξ_c^+ \to Ξ^- π^+ π^+) = [2.86 \pm 1.21(\rm stat.) \pm 0.38(\rm syst.)]\%$ and ${\cal B}(Ξ_c^+ \to p K^- π^+)=[0.45 \pm 0.21(\rm stat.) \pm 0.07(\rm syst.)]\%$. Our result for ${\cal B}(Ξ_c^+ \to Ξ^- π^+ π^+)$ can be combined with $Ξ_c^+$ branching fractions measured relative to $Ξ_c^+ \to Ξ^- π^+ π^+$ to set the absolute scale for many $Ξ_c^+$ branching fractions.

hep-ex↗

arXiv2019

Role of the V-V dimerization in insulator-metal transition and optical transmittance of pure and doped VO2 thin films

Insulator to metal (IMT) transition (T$_t$ $\sim$ 341 K) in the VO2 accompanies transition from an infrared (IR) transparent to IR opaque phase. Tailoring of the IMT and associated IR switching behavior can offer potential thermochromic applications. Here we report on effects of the W and the Tb doping on the IMT and associated structural, electronic structure and optical properties of the VO2 thin film. Our results show that the W doping significantly lowers IMT temperature ($\sim$ 292 K to $\sim$ 247 K for 1.3\% W to 3.7\% W) by stabilizing the metallic rutile, $\it{R}$, phase while Tb doping does not alter the IMT temperature much and retains the insulating monoclinic, $\it{M1}$, phase at room temperature. It is observed that the W doping albeit significantly reduces the IR switching temperature but is detrimental to the solar modulation ability, contrary to the Tb doping effects where higher IR switching temperature and solar modulation ability is observed. The IMT behavior, electrical conductivity and IR switching behavior in the W and the Tb doped thin films are found to be directly associated with the spectral changes in the V 3$\it{d_{\|}}$ states.

cond-mat.mtrl-sci↗

arXiv2019

Search for $B^0 \to X(3872) γ$

We report the results of a search for the decay $B^0 \to X(3872)(\to J/ψπ^+ π^-) γ$. The analysis is performed on a data sample corresponding to an integrated luminosity of $711\,{\rm fb}^{-1}$ and containing $772 \times 10^6 B\bar{B}$ pairs, collected with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider running at the $Υ(4S)$ resonance energy. We find no evidence for a signal and place an upper limit of $\mathcal{B}(B^0 \to X(3872)γ)\times \mathcal{B}(X(3872) \to J/ψπ^+ π^-) < 5.1 \times 10^{-7}$ at 90% confidence level.

hep-ex↗

arXiv2019

Evidence for $B^+ \rightarrow h_c K^+$ and observation of $η_c(2S) \to p \bar{p} π^+ π^-$

A search for the decays $B^+ \rightarrow h_c K^+$ and $B^0 \rightarrow h_c K_S^0$ is performed. Evidence for the decay $B^+ \rightarrow h_c K^+$ is found; its significance is $4.8σ$. No evidence is found for $B^0 \rightarrow h_c K_S^0$. The branching fraction for $B^+ \rightarrow h_c K^+$ is measured to be $(3.7^{+1.0}_{-0.9}{}^{+0.8}_{-0.8}) \times 10^{-5}$; the upper limit for the $B^0 \rightarrow h_c K_S^0$ branching fraction is $1.4 \times 10^{-5}$ at $90\%$ C.L. In addition, a study of the $p \bar{p} π^+ π^-$ invariant mass distribution in the channel $B^+ \to (p \bar{p} π^+ π^-) K^+$ results in the first observation of the decay $η_c(2S) \to p \bar{p} π^+ π^-$ with $12.1σ$ significance. The analysis is based on the 711 $\mathrm{fb}^{-1}$ data sample collected by the Belle detector at the asymmetric-energy $e^+ e^-$ collider KEKB at the $Υ(4S)$ resonance.

hep-ex↗

arXiv2019

Search for $Ω(2012)\to KΞ(1530) \to KπΞ$ at Belle

Using data samples of $e^+e^-$ collisions collected at the $Υ(1S)$, $Υ(2S)$, and $Υ(3S)$ resonances with the Belle detector, we search for the three-body decay of the $Ω(2012)$ baryon to $KπΞ$. This decay is predicted to dominate for models describing the $Ω(2012)$ as a $KΞ(1530)$ molecule. No significant $Ω(2012)$ signals are observed in the studied channels, and 90\% credibility level upper limits on the ratios of the branching fractions relative to $K Ξ$ decay modes are obtained.

hep-ex↗

arXiv2019

Search for $X(3872)$ and $X(3915)$ decay into $χ_{c1} π^0$ in $B$ decays at Belle

We report a search for $X(3872)$ and $X(3915)$ in $B^+ \to χ_{c1} π^0 K^+$ decays. We set an upper limit of $\mathcal{B}(B^+ \to X(3872) K^+) \times \mathcal{B}(X(3872) \to χ_{c1} π^0)$ $ < 8.1 \times 10^{-6}$ and $\mathcal{B}(B^+ \to X(3915) K^+) \times \mathcal{B}(X(3915) \to χ_{c1} π^0)$ $ < 3.8 \times 10^{-5}$ at 90\% confidence level. We also measure $\mathcal{B}(X(3872) \to χ_{c1} π^0)/\mathcal{B}(X(3872) \to J/ψπ^+ π^-) < 0.97$ at 90\% confidence level. The results reported here are obtained from $772 \times 10^{6}$ $B\overline{B}$ events collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider.

hep-ex↗