1. Measurement of branching fractions for $B \to J/\psi \eta K$ decays and search for a narrow resonance in the $J/\psi \eta$ final stateT. Iwashita, Marko Bračko, Boštjan Golob, Jure Klučar, Samo Korpar, Peter Križan, Rok Pestotnik, Marko Petrič, Marko Starič, Luka Šantelj, Anže Zupanc, 2014, original scientific article Abstract: We report an observation of the $B^{\pm } \to J/\psi \eta K^{\pm }$ and $B^0 \to J/\psi \eta K^0_S$ decays using $772\times 10^{6}B\overline {B}$ pairs collected at the $\Upsilon (4S)$ resonance with the Belle detector at the KEKB asymmetricenergy $e^+e^$ collider. We obtain the branching fractions ${\mathcal B}(B^{\pm }\rightarrow J/\psi \eta K^{\pm })=(1.27\pm 0.11(\hbox {stat.})\pm 0.11(\hbox {syst.}))\times 10^{4}$ and ${\mathcal B}(B^0\to J/\psi \eta K^0_S)=(5.22 \pm 0.78 (\hbox {stat.}) \pm 0.49 (\hbox {syst.}))\times 10^{5}$. We search for a new narrow charmonium(like) state $X$ in the $ J/\psi \eta$ mass spectrum and find no significant excess. We set upper limits on the product of branching fractions, ${\mathcal B}(B^\pm \to XK^\pm){\mathcal B}(X \to J/\psi \eta)$, at $3872\,\hbox {MeV}\,c^{2}$ where a $C$odd partner of $X(3872)$ may exist, at $\psi (4040)$ and $\psi (4160)$ assuming their known mass and width, and over a range from 3.8 to $4.8\,\hbox {GeV}\,c^{2}$. The obtained upper limits at 90% confidence level for $X^{C\hbox {}{\rm odd}}(3872)$, $\psi (4040)$, and $\psi (4160)$ are $3.8\times 10^{6}$, $15.5\times 10^{6}$, and $7.4\times 10^{6}$, respectively. Keywords: C07, C21, particle properties, lepton collider experiments, experimental particle physics Published: 21.07.2017; Views: 545; Downloads: 103 Full text (372,20 KB) This document has many files! More...

2. Highstatistics study of $K^0_S K^0_S$ pair production in twophoton collisionsS. Uehara, Marko Bračko, Boštjan Golob, Jure Klučar, Samo Korpar, Peter Križan, Rok Pestotnik, Marko Petrič, Marko Starič, Luka Šantelj, Anže Zupanc, 2013, original scientific article Abstract: We report a highstatistics measurement of the differential cross section of the process $\gamma \gamma \to K^0_S K^0_S$ in the range $1.05\,{\mathrm {GeV}} \leq W \leq 4.00$ , where W is the centerofmass energy of the colliding photons, using 972 $^{1}$ of data collected with the Belle detector at the KEKB asymmetricenergy e+e− collider operated at and near the $\Upsilon$resonance region. The differential cross section is fitted by parameterized S, $D_0$, $D_2$, $G_0$, and $G_2$wave amplitudes. In the $D_2$ wave, the $f_2$(1270), $a_2$(1320), and $f′_2$(1525) are dominant and a resonance, the $f_2$(2200), is also present. The $f_0$(1710) and possibly the $f_0$(2500) are seen in the S wave. The mass, total width, and product of the twophoton partial decay width and decay branching fraction to the $K \bar {K}$ state $\Gamma _{\gamma \gamma }\mathcal {B}(K \bar {K})$ are extracted for the $f′_2$(1525), $f_0$(1710), $f_2$(2200), and $f_0$(2500). The destructive interference between the $f_2$(1270) and $a_2$(1320) is confirmed by measuring their relative phase. The parameters of the charmonium states $\chi _{c0}$ and $\chi _{c2}$ are updated. Possible contributions from the $\chi _{c0}(2P)$ and $\chi _{c2}(2P)$ states are discussed. A new upper limit for the branching fraction of the P and CPviolating decay channel $\eta _c \to K^0_S K^0_S$ is reported. The detailed behavior of the cross section is updated and compared with QCDbased calculations. Keywords: C00, C05, C07, C21, quantum chromodynamics, quark model, particle properties, lepton collider experiments, experimental particle physics Published: 21.07.2017; Views: 553; Downloads: 59 Full text (2,28 MB) This document has many files! More...

3. First modelindependent Dalitz analysis of $B^0 \to D^0K^{\ast 0}$, $D\to K_S^0\pi ^+\pi ^$ decayK. Negishi, Jyoti Prakash Biswal, Marko Bračko, Boštjan Golob, Samo Korpar, Peter Križan, Tara Nanut, Rok Pestotnik, Marko Petrič, Eva Ribežl, Samo Stanič, Marko Starič, Luka Šantelj, Anže Zupanc, 2016, original scientific article Abstract: We report a measurement of the amplitude ratio $r_S$ of $B^0 \to D^0K^{\ast 0}$ and $B^0 \to \bar {D^0}K^{\ast 0}$ decays with a Dalitz analysis of $D\to K_S^0\pi ^+\pi ^$ decays, for the first time using a modelindependent method. We set an upper limit $r_S < 0.87$ at the 68% confidence level, using the full data sample of $711\,{\rm fb}^{1}$ corresponding to $772\times 10^6$ $B\bar {B}$ pairs collected at the $\Upsilon (4S)$ resonance with the Belle detector at the KEKB $e^+e^$ collider. This result is obtained from observables $x_ = +0.4 ^{+1.0 +0.0}_{0.6 0.1} \pm 0.0$, $y_ = 0.6 ^{+0.8 +0.1}_{1.0 0.0} \pm 0.1$, $x_+ = +0.1 ^{+0.7 +0.0}_{0.4 0.1} \pm 0.1$, and $y_+ = +0.3 ^{+0.5 +0.0}_{0.8 0.1} \pm 0.1$, where $x_\pm = r_S \cos (\delta _S \pm \phi _3)$, $y_\pm = r_S \sin (\delta _S \pm \phi _3)$, and $\phi _3\ (\delta _S)$ is the weak (strong) phase difference between $B^0 \to D^0K^{\ast 0}$ and $B^0 \to \bar {D^0}K^{\ast 0}$. Keywords: CO2, CO3, CabibboKobayashiMaskawa quarkmixing matrix, CP violation, experimental particle physics Published: 21.07.2017; Views: 563; Downloads: 103 Full text (555,01 KB) This document has many files! More...

4. The physics of the B factoriesAdrian Bevan, Boštjan Golob, Peter Križan, Jure Zupan, Anže Zupanc, Marko Starič, Urban Bitenc, Ilija Bizjak, Marko Bračko, Saša Fratina, Andrej Gorišek, Jure Klučar, Samo Korpar, Rok Pestotnik, Marko Petrič, Luka Šantelj, Peter Smerkol, Samo Stanič, Tomi Živko, Dejan Žontar, 2015, scientific monograph Keywords: experimental particle physics, elementary particles, B mesons, B factories Published: 26.06.2017; Views: 636; Downloads: 206 Full text (31,86 MB) This document has many files! More...
