Sneha Malde

Abstract:

We report a study of the semileptonic decay $D^0\to {\overline{K}}^0{\pi }^{-}{\mu }^{+}{\nu }_{\mu }$ based on a sample of $7.9{\mathrm{fb}}^{-1}$ of $e^{+}{e}^{-}$ annihilation data collected at a center-of-mass energy of 3.773 GeV with the BESIII detector at the BEPCII collider. The branching fraction of the decay is measured for the first time to be $\mathcal{B}(D^0\to {\overline{K}}^0{\pi }^{-}{\mu }^{+}{\nu }_{\mu })=(1.373\pm 0.020_{\mathrm{stat}}\pm 0.023_{\mathrm{syst}})\%$ , where the first uncertainty is statistical and the second is systematic. Based on the investigation of the decay dynamics, we find that the decay is dominated by the $K^{*}(892{)}^{-}$ resonance with the branching fraction measured to be $\mathcal{B}(D^0\to K^{*}(892{)}^{-}{\mu }^{+}{\nu }_{\mu })=(1.948\pm 0.033_{\mathrm{stat}}\pm 0.036_{\mathrm{syst}})\%$ . We also determine the hadronic form factors for the $D^0\to K^{*}(892{)}^{-}{\mu }^{+}{\nu }_{\mu }$ decay to be $r_V=V(0)/A_1(0)=1.46\pm 0.11_{\mathrm{stat}}\pm 0.04_{\mathrm{syst}}$ , $r_2=A_2(0)/A_1(0)=0.71\pm 0.08_{\mathrm{stat}}\pm 0.03_{\mathrm{syst}}$ , and $A_1(0)=0.609\pm 0.008_{\mathrm{stat}}\pm 0.008_{\mathrm{syst}}$ , where $V(0)$ is the vector form factor and $A_{1,2}(0)$ are the axial-vector form factors evaluated at $q^2=0$ . The $A_1(0)$ is measured for the first time in $D^0\to K^{*}(892{)}^{-}{\mu }^{+}{\nu }_{\mu }$ decay. Averaging the form factor parameters that we reported previously in $D^0\to K^{*}(892{)}^{-}(\to {\overline{K}}^0{\pi }^{-})e^{+}{\nu }_e$ and $D^0\to K^{*}(892{)}^{-}(\to K^{-}{\pi }^0){\mu }^{+}{\nu }_{\mu }$ decays, we obtain $r_V=1.456\pm 0.040_{\mathrm{stat}}\pm 0.016_{\mathrm{syst}}$ , $r_2=0.715\pm 0.031_{\mathrm{stat}}\pm 0.014_{\mathrm{stat}}$ , and $A_1(0)=0.614\pm 0.005_{\mathrm{stat}}\pm 0.004_{\mathrm{syst}}$ . This is the most precise determination of the form factor parameters to date measured in $D\to K^{*}(892)$ transitions, which provide the most stringent test on various theoretical models.

Abstract:

By analyzing a data sample containing events taken with the BESIII detector at the BEPCII storage ring in 2009, the resonance parameters are precisely measured using events. The mass of is determined to be ) MeV/ , and its full width is , where the first uncertainty is statistical, the second systematic, and the third for mass comes from mass uncertainty. These measurements improve the precision of mass by a factor of four and width by one order of magnitude over the previous individual measurements, and significantly boost our knowledge about the charmonium spectrum. Together with additional data events taken in 2012, the decay branching fractions of are measured as well, with precision improved by a factor of three compared to previous measurements. These decay branching fractions provide important inputs for the study of glueballs.

Abstract:

Using $e^{+}{e}^{-}$ data taken at the center-of-mass energy of 3.773 GeV with the BESIII detector, corresponding to an integrated luminosity of $20.3{\mathrm{fb}}^{-1}$ , we report the first measurement of the decay dynamics of the semileptonic decays $D^{+(0)}\to K^{-}{\pi }^{+}{\pi }^{0(-)}{e}^{+}{\nu }_e$ . The amplitude analysis gives the hadronic form factors of the semileptonic $D$ transitions into the axial-vector meson ${\overline{K}}_1(1270)$ to be $r_A=(-11.2\pm {1.0}_{\mathrm{stat}}\pm {0.9}_{\mathrm{syst}})\times {10}^{-2}$ and $r_V=(-4.3\pm {1.0}_{\mathrm{stat}}\pm {2.5}_{\mathrm{syst}})\times {10}^{-2}$ . This is the first in the semileptonic decays of heavy mesons into axial-vector mesons. The angular analysis yields an up-down asymmetry ${\mathcal{A}}_{\mathrm{ud}}^{\prime }=0.01\pm 0.11$ , which is consistent with the standard model prediction. In addition, the branching fractions of $D^{+}\to {\overline{K}}_1(1270{)}^0{e}^{+}{\nu }_e$ and $D^0\to K_1(1270{)}^{-}{e}^{+}{\nu }_e$ are determined with improved precision to be $(2.27\pm 0.11_{\mathrm{stat}}\pm 0.07_{\mathrm{syst}}\pm 0.07_{\text{input}})\times {10}^{-3}$ and $(1.02\pm 0.06_{\mathrm{stat}}\pm 0.06_{\mathrm{syst}}\pm 0.03_{\text{input}})\times {10}^{-3}$ , respectively. No significant signals of $D^{+}\to {\overline{K}}_1(1400{)}^0{e}^{+}{\nu }_e$ and $D^0\to K_1(1400{)}^{-}{e}^{+}{\nu }_e$ are observed and their branching fraction upper limits are set as $1.4\times {10}^{-4}$ and $0.7\times {10}^{-4}$ at 90% confidence level, respectively.

Abstract:

A study on the Bose-Einstein correlations for triplets of same-sign pions is presented. The analysis is performed using proton-proton collisions at a centre-of-mass energy of s = 7 TeV, recorded by the LHCb experiment, corresponding to an integrated luminosity of 1.0 fb−1. For the first time, the results are interpreted in the core-halo model. The parameters of the model are determined in regions of charged-particle multiplicity. This measurement provides insight into the nature of hadronisation in terms of coherence, being consistent with the presence of coherent emission of pions.

Abstract:

Using $e^{+}{e}^{-}$ collision data collected with the BESIII detector operating at the Beijing electron positron collider, the cross section of $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}{h}_c$ is measured at 59 points with center-of-mass energy $\sqrt{s}$ ranging from 4.009 to 4.950 GeV with a total integrated luminosity of $22.2{\mathrm{fb}}^{-1}$ . The cross section between 4.3 and 4.45 GeV exhibits a plateaulike shape and drops sharply around 4.5 GeV, which cannot be described by two resonances only. Three coherent Breit-Wigner functions are used to parametrize the $\sqrt{s}$ -dependent cross section line shape. The masses and widths are determined to be $M_1=({4223.6}_{-3.7-2.9}^{+3.6+2.6})\mathrm{MeV}/c^2$ , ${\mathrm{\Gamma }}_1=({58.5}_{-11.4-6.5}^{+10.8+6.7})\mathrm{MeV}$ , $M_2=({4327.4}_{-18.8-9.3}^{+20.1+10.7})\mathrm{MeV}/c^2$ , ${\mathrm{\Gamma }}_2=({244.1}_{-27.1-18.3}^{+34.0+24.2})\mathrm{MeV}$ , and $M_3=({4467.4}_{-5.4-2.7}^{+7.2+3.2})\mathrm{MeV}/c^2$ , and ${\mathrm{\Gamma }}_3=({62.8}_{-14.4-7.0}^{+19.2+9.9})\mathrm{MeV}$ . The first uncertainties are statistical and the second are systematic. The inclusion of the relatively narrower third component proves crucial for reproducing the drop at around 4.5 GeV. The statistical significance of the three-resonance assumption over the two-resonance assumption is greater than $5\sigma$ .