arXiv subjects

I. Badhrees

Publications and source records attributed to I. Badhrees.

At least 55 records · Page 3Linked to original sources

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

Characterization of the Hamamatsu VUV4 MPPCs for nEXO

In this paper we report on the characterization of the Hamamatsu VUV4 (S/N: S13370-6152) Vacuum Ultra-Violet (VUV) sensitive Silicon Photo-Multipliers (SiPMs) as part of the development of a solution for the detection of liquid xenon scintillation light for the nEXO experiment. Various SiPM features, such as: dark noise, gain, correlated avalanches, direct crosstalk and Photon Detection Efficiency (PDE) were measured in a dedicated setup at TRIUMF. SiPMs were characterized in the range $163 \text{ } \text{K} \leq \text{T}\leq 233 \text{ } \text{K}$. At an over voltage of $3.1\pm0.2$ V and at $\text{T}=163 \text{ }\text{K}$ we report a number of Correlated Avalanches (CAs) per pulse in the $1 \upmu\text{s}$ interval following the trigger pulse of $0.161\pm0.005$. At the same settings the Dark-Noise (DN) rate is $0.137\pm0.002 \text{ Hz/mm}^{2}$. Both the number of CAs and the DN rate are within nEXO specifications. The PDE of the Hamamatsu VUV4 was measured for two different devices at $\text{T}=233 \text{ }\text{K}$ for a mean wavelength of $189\pm7\text{ nm}$. At $3.6\pm0.2$ V and $3.5\pm0.2$ V of over voltage we report a PDE of $13.4\pm2.6\text{ }\%$ and $11\pm2\%$, corresponding to a saturation PDE of $14.8\pm2.8\text{ }\%$ and $12.2\pm2.3\%$, respectively. Both values are well below the $24\text{ }\%$ saturation PDE advertised by Hamamatsu. More generally, the second device tested at $3.5\pm0.2$ V of over voltage is below the nEXO PDE requirement. The first one instead yields a PDE that is marginally close to meeting the nEXO specifications. This suggests that with modest improvements the Hamamatsu VUV4 MPPCs could be considered as an alternative to the FBK-LF SiPMs for the final design of the nEXO detector.

astro-ph.IM↗

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↗

arXiv2019

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

We report a measurement of 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 $\mathcal{R}(D^{\ast}) = {\cal B}(\bar{B} \to D^* τ^- \barν_τ)/{\cal B}(\bar{B} \to D^* \ell^- \barν_{\ell})$, where $\ell$ denotes an electron or a muon. The results are based on a data sample containing $772\times10^6$ $B\bar{B}$ events recorded at the $Υ(4S)$ resonance with the Belle detector at the KEKB $e^+ e^-$ collider. The analysis utilizes a method where 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 $\mathcal{R}(D^{\ast})= 0.283 \pm 0.018 \pm 0.014$, where the first uncertainties are statistical and the second are systematic. These results are in agreement with the Standard Model predictions within $0.2$ and $1.1$ standard deviations, respectively, while their combination agrees with the Standard Model predictions within $1.2$ standard deviations.

hep-ex↗

arXiv2019

Observation of $e^+e^-\toπ^+π^-π^0χ_{b1,2}(1P)$ and search for $e^+e^-\toϕχ_{b1,2}(1P)$ at $\sqrt{s}=$10.96---11.05 GeV

We report searches for the processes $e^+e^-\toπ^+π^-π^0χ_{bJ}$ and $e^+e^-\toϕχ_{bJ}$ (J=1,2) based on data samples collected by the Belle experiment at the KEKB collider. We report the first observation of the process $e^+e^-\to (π^+π^-π^0)_{\rm non-ω}χ_{b1}$ and first evidence for $e^+e^-\toωχ_{bJ}$ in the vicinity of the $Υ(11020)$ resonance, with center-of-mass energies from 10.96 to 11.05~GeV. The significances for $(π^+π^-π^0)_{\rm non-ω}χ_{b1}$ and $ωχ_{bJ}$ are greater than $5.3σ$ and $4.0σ$, respectively. We also investigate the energy dependence of the $e^+e^-\toπ^+π^-π^0χ_{bJ}$ cross section, but we cannot determine whether the contributions are from the $Υ(10860)$ and $Υ(11020)$ resonances or non-resonant continuum processes. The signals for $e^+e^-\to ϕχ_{bJ}$ are not significant, and the upper limits of the Born cross sections at the 90\% confidence level are $0.7$ and $1.0$~pb for $e^+e^-\to ϕχ_{b1}$ and $ϕχ_{b2}$, respectively, for center-of-mass energies from 10.96 to 11.05~GeV.

hep-ex↗

arXiv2019

Measurement of the CKM Matrix Element $|V_{cb}|$ from $B^{0} \to D^{*-} \ell^+ ν_\ell$ at Belle

We present a new measurement of the CKM matrix element $|V_{cb}|$ from $B^{0} \to D^{*-} \ell^+ ν_\ell$ decays, reconstructed with the full Belle data set of $711 \, \rm fb^{-1}$ integrated luminosity. Two form factor parameterizations, originally conceived by the Caprini-Lellouch-Neubert (CLN) and the Boyd, Grinstein and Lebed (BGL) groups, are used to extract the product $\mathcal{F}(1)η_{\rm EW}|V_{cb}|$ and the decay form factors, where $\mathcal{F}(1)$ is the normalization factor and $η_{\rm EW}$ is a small electroweak correction. In the CLN parameterization we find $\mathcal{F}(1)η_{\rm EW}|V_{cb}| = (35.06 \pm 0.15 \pm 0.56) \times 10^{-3}$, $ρ^{2}=1.106 \pm 0.031 \pm 0.007$, $R_{1}(1)=1.229 \pm 0.028 \pm 0.009$, $R_{2}(1)=0.852 \pm 0.021 \pm 0.006$. For the BGL parameterization we obtain $\mathcal{F}(1)η_{\rm EW}|V_{cb}|= (34.93 \pm 0.23 \pm 0.59)\times 10^{-3}$, which is consistent with the World Average when correcting for $\mathcal{F}(1)η_{\rm EW}$. The branching fraction of $B^{0} \to D^{*-} \ell^+ ν_\ell$ is measured to be $\mathcal{B}(B^{0}\rightarrow D^{*-}\ell^{+}ν_{\ell}) = (4.90 \pm 0.02 \pm 0.16)\%$. We also present a new test of lepton flavor universality violation in semileptonic $B$ decays, $\frac{{\cal B }(B^0 \to D^{*-} e^+ ν)}{{\cal B }(B^0 \to D^{*-} μ^+ ν)} = 1.01 \pm 0.01 \pm 0.03~$. The errors correspond to the statistical and systematic uncertainties respectively. This is the most precise measurement of $\mathcal{F}(1)η_{\rm EW}|V_{cb}|$ and form factors to date and the first experimental study of the BGL form factor parameterization in an experimental measurement.

hep-ex↗

arXiv2019

Measurement of branching fraction and final-state asymmetry for the $\bar{B}^{0}\to K^{0}_{S}K^{\mp}π^{\pm}$ decay

We report a measurement of the branching fraction and final-state asymmetry for the $\bar{B}^{0}\to K^{0}_{S}K^{\mp}π^{\pm}$ decays. The analysis is based on a data sample of 711 $\rm{fb}^{-1}$ collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}e^{-}$ collider. We obtain a branching fraction of $(3.60\pm0.33\pm0.15)\times10^{-6}$ and a final-state asymmetry of $(-8.5\pm8.9\pm0.2)\%$, where the first uncertainties are statistical and the second are systematic. Hints of peaking structures are seen in the differential branching fractions measured as functions of Dalitz variables.

hep-ex↗

arXiv2019

Evidence for the decay $B^0\to p\bar{p}π^0$

We report a search for the charmless baryonic decay $B^0\to p\bar{p}π^0$ with a data sample corresponding to an integrated luminosity of 711~$\rm fb^{-1}$ containing $(772\pm 10)\times 10^6$ $B^0\bar{B}^0$ pairs. The data was collected by the Belle experiment running on the $Υ(4S)$ resonance at the KEKB $e^+e^-$ collider. We measure a branching fraction $\mathcal{B}(B^0\to p\bar{p}π^0)= (5.0\pm1.8\pm0.6 )\times 10^{-7}$, where the first uncertainty is statistical and the second is systematic. The signal has a significance of 3.1 standard deviations and constitutes the first evidence for this decay mode. We also search for the intermediate two-body decays $B^{0}\toΔ^+\bar{p}$ and $B^0\to\barΔ^-p$, and set an upper limit on the branching fraction: $\mathcal{B}(B^0\to Δ^+\bar{p})+\mathcal{B}(B^0\to\barΔ^-p)<1.6\times10^{-6}$ at 90% confidence level.

hep-ex↗

arXiv2019

VUV-sensitive Silicon Photomultipliers for Xenon Scintillation Light Detection in nEXO

Future tonne-scale liquefied noble gas detectors depend on efficient light detection in the VUV range. In the past years Silicon Photomultipliers (SiPMs) have emerged as a valid alternative to standard photomultiplier tubes or large area avalanche photodiodes. The next generation double beta decay experiment, nEXO, with a 5 tonne liquid xenon time projection chamber, will use SiPMs for detecting the $178\,\text{nm}$ xenon scintillation light, in order to achieve an energy resolution of $σ/ Q_{ββ} = 1\, \%$. This paper presents recent measurements of the VUV-HD generation SiPMs from Fondazione Bruno Kessler in two complementary setups. It includes measurements of the photon detection efficiency with gaseous xenon scintillation light in a vacuum setup and dark measurements in a dry nitrogen gas setup. We report improved photon detection efficiency at $175\,\text{nm}$ compared to previous generation devices, that would meet the criteria of nEXO. Furthermore, we present the projected nEXO detector light collection and energy resolution that could be achieved by using these SiPMs.

physics.ins-det↗

arXiv2019

Measurement of the $D^{\ast-}$ polarization in the decay $B^0 \to D^{\ast -}τ^+ν_τ$

We report the first measurement of the $D^{\ast -}$ meson polarization in the decay $B^0 \to D^{*-} τ^+ν_τ$ using the full data sample of 772$\times 10^6$ $B\bar{B}$ pairs recorded with the Belle detector at the KEKB electron-positron collider. Our result, $F_L^{D^\ast} = 0.60 \pm 0.08 ({\rm stat}) \pm 0.04 ({\rm sys})$, where $F_L^{D^\ast}$ denotes the $D^{\ast-}$ meson longitudinal polarization fraction, agrees within about $1.7$ standard deviations of the standard model prediction.

hep-ex↗

arXiv2019

First measurements of absolute branching fractions of $Ξ_c^0$ at Belle

We present the first measurements of absolute branching fractions of $Ξ_c^0$ decays into $Ξ^- π^+$, $ΛK^- π^+$, and $p K^- K^- π^+$ final states. The measurements are made using a data set comprising $(772\pm 11)\times 10^{6}$ $B\bar{B}$ pairs collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB $e^+e^-$ collider. We first measure the absolute branching fraction for $B^- \to \barΛ_c^- Ξ_c^0$ using a missing-mass technique; the result is ${\cal B}(B^- \to \barΛ_c^- Ξ_c^0) = (9.51 \pm 2.10 \pm 0.88) \times 10^{-4}$. We subsequently measure the product branching fractions ${\cal B}(B^- \to \barΛ_c^- Ξ_c^0){\cal B}(Ξ_c^0 \to Ξ^- π^+)$, ${\cal B}( B^- \to \barΛ_c^- Ξ_c^0) {\cal B}(Ξ_c^0 \to ΛK^- π^+)$, and ${\cal B}( B^- \to \barΛ_c^- Ξ_c^0) {\cal B}(Ξ_c^0 \to p K^- K^- π^+)$ with improved precision. Dividing these product branching fractions by the result for $B^- \to \barΛ_c^- Ξ_c^0$ yields the following branching fractions: ${\cal B}(Ξ_c^0 \to Ξ^- π^+)= (1.80 \pm 0.50 \pm 0.14)\%$, ${\cal B}(Ξ_c^0 \to ΛK^- π^+)=(1.17 \pm 0.37 \pm 0.09)\%$, and ${\cal B}(Ξ_c^0 \to p K^- K^- π^+)=(0.58 \pm 0.23 \pm 0.05)\%.$ For the above branching fractions, the first uncertainties are statistical and the second are systematic. Our result for ${\cal B}(Ξ_c^0 \to Ξ^- π^+)$ can be combined with $Ξ_c^0$ branching fractions measured relative to $Ξ_c^0 \to Ξ^- π^+$ to yield other absolute $Ξ_c^0$ branching fractions.

hep-ex↗

arXiv2019

Search for $CP$ violation with kinematic asymmetries in the $D^0 \to K^+ K^- π^+ π^-$ decay

We search for $CP$ violation in the singly-Cabibbo-suppressed decay $D^{0}\rightarrow K^{+}K^{-}π^{+}π^{-}$ using data corresponding to an integrated luminosity of $988\text{ }{\rm fb}^{-1}$ collected by the Belle detector at the KEKB $e^{+}e^{-}$ collider. We measure a set of five kinematically dependent $CP$ asymmetries, of which four asymmetries are measured for the first time. The set of asymmetry measurements can be sensitive to $CP$ violation via interference between the different partial-wave contributions to the decay and performed on other pseudoscalar decays. We find no evidence of $CP$ violation.

hep-ex↗

arXiv2019

Measurement of time-dependent $CP$ violation in $B^0 \to K^0_S π^0 π^0$ decays

We report a measurement of time-dependent $CP$ violation in $B^0 \to K^0_S π^0 π^0$ decays using a data sample of $772 \times 10^6$ $B\bar{B}$ pairs collected by the Belle experiment runnin g at the $Υ(4S)$ resonance at the KEKB $e^+ e^-$ collider. This decay proceeds mainly via a $b\to sd\bar{d}$ "penguin" amplitude. The results are $\sin 2ϕ^{\rm eff}_1 = 0.92^{+0.27}_{-0.31}~$ (stat.) $\pm 0.11$ (syst.) and $\mathcal{A} = 0.28 \pm 0.21$ (stat.) $\pm 0.04$ (syst.), which are the most precise measurements of $CP$ violati on in this decay mode to date. The value for the $CP$-violating parameter $\sin 2ϕ^{\rm eff}_1$ is consistent with that obtained using decay modes proceeding via a $b\to c\bar{c}s$ "tree" amplitude.

hep-ex↗

arXiv2018

Search for the rare decay of $B^+ \to \ell^{\,+} ν_{\ell} γ$ with improved hadronic tagging

We present the result of the search for the rare $B$ meson decay of $B^+ \to \ell^{\,+} ν_{\ell} γ$ with $\ell =e,μ$. For the search the full data set recorded by the Belle experiment of $711 \, \mathrm{fb}^{-1}$ integrated luminosity near the $Υ(4S)$ resonance is used. Signal candidates are reconstructed for photon energies $E_γ$ larger than $1 \, \mathrm{GeV}$ using a novel multivariate tagging algorithm. The novel algorithm fully reconstructs the second $B$ meson produced in the collision using hadronic modes and was specifically trained to recognize the signal signature in combination with hadronic tag-side $B$ meson decays. This approach greatly enhances the performance. Background processes that can mimic this signature, mainly charmless semileptonic decays and continuum processes, are suppressed using multivariate methods. The number of signal candidates is determined by analyzing the missing mass squared distribution as inferred from the signal side particles and the kinematic properties of the tag-side $B$ meson. No significant excess over the background-only hypothesis is observed and upper limits on the partial branching fraction $ Δ\mathcal{B} $ with $E_γ> 1 \, \mathrm{GeV}$ individually for electron and muon final states as well as for the average branching fraction of both lepton final states are reported. We find a Bayesian upper limit of $Δ\mathcal{B}( B^{+} \to \ell^{\, +} ν_{\ell} γ) < 3.0 \times 10^{-6}$ at 90% CL and also report an upper limit on the first inverse moment of the light-cone distribution amplitude of the $B$ meson of $λ_B$ at 90% CL.

hep-ex↗

arXiv2018

Measurements of branching fraction and direct $C\!P$ asymmetry in $B^{\pm}\to K^{0}_{S}K^{0}_{S}K^{\pm}$ and a search for $B^{\pm}\to K^{0}_{S}K^{0}_{S}π^{\pm}$

We study charmless hadronic decays of charged $B$ mesons to the final states $K^{0}_{S}K^{0}_{S}K^{\pm}$ and $K^{0}_{S}K^{0}_{S}π^{\pm}$ using a $711 fb^{-1}$ data sample that contains $772\times 10^6$ $B\bar{B}$ pairs, and was collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}e^{-}$ collider. For $B^{\pm}\to K^{0}_{S}K^{0}_{S}K^{\pm}$, the measured branching fraction and direct $CP$ asymmetry are $[10.42\pm0.43(stat)\pm 0.22(syst)]\times10^{-6}$ and [$+1.6\pm3.9(stat)\pm 0.9(syst)$]%, respectively. In the absence of a statistically significant signal for $B^{\pm}\to K^{0}_{S}K^{0}_{S}π^{\pm}$, we obtain a 90% confidence-level upper limit on its branching fraction as $8.7 \times10^{-7}$.

hep-ex↗

arXiv2018

Measurement of the branching fraction and time-dependent $CP$ asymmetry for $B^0\to J/ψπ^0$ decays

We measure the branching fraction and time-dependent $CP$-violating asymmetry for $B^0\to J/ψπ^0$ decays using a data sample of 711 ${\rm fb^{-1}}$ collected on the $Υ(4S)$ resonance by the Belle experiment running at the KEKB $e^+e^-$ collider. The branching fraction is measured to be $\mathcal{B}(B^0\to J/ψπ^0) = [1.62\,\pm 0.11~({\rm stat}) \pm0.07~({\rm syst})]\times 10^{-5}$, which is the most precise measurement to date. The measured $CP$ asymmetry parameters are $\mathcal{S} = -0.59\,\pm 0.19~({\rm stat}) \pm 0.03~({\rm syst})$ and $\mathcal{A} = -0.15\,\pm 0.14~({\rm stat})\,^{+0.04}_{-0.03}~({\rm syst})$. The mixing-induced $CP$ asymmetry ($\mathcal{S}$) differs from the case of no $CP$ violation by 3.0 standard deviations, and the direct $CP$ asymmetry ($\mathcal{A}$) is consistent with zero.

hep-ex↗

arXiv2018

Imaging individual barium atoms in solid xenon for barium tagging in nEXO

The search for neutrinoless double beta decay probes the fundamental properties of neutrinos, including whether or not the neutrino and antineutrino are distinct. Double beta detectors are large and expensive, so background reduction is essential for extracting the highest sensitivity. The identification, or 'tagging', of the $^{136}$Ba daughter atom from double beta decay of $^{136}$Xe provides a technique for eliminating backgrounds in the nEXO neutrinoless double beta decay experiment. The tagging scheme studied in this work utilizes a cryogenic probe to trap the barium atom in solid xenon, where the barium atom is tagged via fluorescence imaging in the solid xenon matrix. Here we demonstrate imaging and counting of individual atoms of barium in solid xenon by scanning a focused laser across a solid xenon matrix deposited on a sapphire window. When the laser sits on an individual atom, the fluorescence persists for $\sim$30~s before dropping abruptly to the background level, a clear confirmation of one-atom imaging. No barium fluorescence persists following evaporation of a barium deposit to a limit of $\leq$0.16\%. This is the first time that single atoms have been imaged in solid noble element. It establishes the basic principle of a barium tagging technique for nEXO.

physics.ins-det↗

arXiv2018

Observation of $B^{+} \rightarrow p\barΛ K^+ K^-$ and $B^{+} \rightarrow \bar{p}ΛK^+ K^+$

We report the study of \OK \ and \SK \ using a $772 \times 10^6$ $B\bar{B}$ pair data sample recorded on the $Υ({\rm 4S})$ resonance with the Belle detector at KEKB. The following branching fractions are measured: $\mathcal{B}$(\OKPHSP) $=$ $(4.22^{+0.45}_{-0.44}\pm 0.51)\times10^{-6}$, $\mathcal{B}$(\SKPHSP) $=$ $(3.81^{+0.39}_{-0.37} \pm 0.45)\times 10^{-6}$, $\mathcal{B}$(\ETACD+c.c.) $=$ $(2.91^{+0.37}_{-0.35}\pm 0.36)\times 10^{-3}$ and $\mathcal{B}$(\PLPHI) $=$ $(8.18 \pm 2.15 \pm 0.79)\times10^{-7}$, where c.c. denotes the corresponding charge-conjugation process. The intermediate resonance decays are excluded in the four-body decay measurements. We also found evidences for $\mathcal{B}$(\ETACS+c.c.) $=$ $(3.59 \pm 1.52 \pm 0.47) \times 10^{-3}$ and $\mathcal{B}$(\LLKO) $=$ $(2.30 \pm 0.65 \pm 0.25) \times 10^{-6}$. No significant signals are found for \JPSIS+c.c. and \LLKS \ ; we set the 90\% confidence level upper limits on their decay branching fractions as $< 1.85\times10^{-3}$ and $< 2.14\times10^{-6}$, respectively.

hep-ex↗