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Measurement of time-dependent CP violation in B 0 → η′K 0 decays
Luka Šantelj, Marko Bračko, Boštjan Golob, Samo Korpar, Peter Križan, Tara Nanut, Rok Pestotnik, Marko Petrič, Eva Ribežl, Marko Starič, Anže Zupanc, 2014, izvirni znanstveni članek

Opis: We present a measurement of the time-dependent CP violation parameters in B0 → η′K0 decays. The measurement is based on the full data sample containing 772 × 10^6 BB pairs collected at the Υ(4S) resonance using the Belle detector at the KEKB asymmetric-energy e+e− collider. The measured values of the mixing-induced and direct CP violation parameters are: sin⁡ 2ϕ1eff=+0.68±0.07±0.03, Aη′K0=+0.03±0.05±0.04, where the first uncertainty is statistical and the second is systematic. The values obtained are the most accurate to date. Furthermore, these results are consistent with our previous measurements and with the world-average value of sin 2ϕ1 measured in B0 → J/ψK0 decays.
Ključne besede: CP violation, CKM angle beta, e+-e- Experiments, B physics
Objavljeno: 27.06.2017; Ogledov: 360; Prenosov: 192
.pdf Celotno besedilo (448,79 KB)
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4.
Search for B decays to final states with the η c meson
A. Vinokurova, Marko Bračko, Boštjan Golob, Samo Korpar, Peter Križan, Rok Pestotnik, Marko Petrič, Eva Ribežl, Samo Stanič, Marko Starič, Luka Šantelj, Anže Zupanc, 2015, izvirni znanstveni članek

Opis: We report a search for B decays to selected final states with the ηc meson: B± → K±ηcπ+π−, B± → K±ηcω, B± → K±ηcη and B± → K±ηcπ0. The analysis is based on 772 × 10^6 B¯B pairs collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e− collider. We set 90% confidence level upper limits on the branching fractions of the studied B decay modes, independent of intermediate resonances, in the range (0.6–5.3)×10^−4. We also search for molecular-state candidates in the D^0 ¯D^∗0 − ¯D^0D^∗0, D^0 ¯D^0 + ¯D^0D^0 and D^∗0¯D^∗0 + ¯D^∗0D^∗0 combinations, neutral partners of the Z(3900)± and Z(4020)±, and a poorly understood state X(3915) as possible intermediate states in the decay chain, and set 90% confidence level upper limits on the product of branching fractions to the mentioned intermediate states and decay branching fractions of these states in the range (0.6–6.9)×10^−5.
Ključne besede: exotics, quarkonium, e+-e- experiments, B physics, particle and resonance production
Objavljeno: 27.06.2017; Ogledov: 368; Prenosov: 208
.pdf Celotno besedilo (129,32 KB)
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5.
Status of the super KEK B factory
Marko Bračko, 2009, objavljeni znanstveni prispevek na konferenci

Opis: We are preparing a major upgrade of the KEKB electron-positron collider, the Super KEK B factory (SuperKEKB) – a project that could detect new phenomena arising from physics beyond the Standard Model by using a large amount of data, corresponding to the integrated luminosity of 50 ab-1. This data set will allow studies of rare processes in B meson decays, D meson decays and τ lepton decays with an unprecedented sensitivity. To achieve the goal of this ambitious project, the design luminosity of the SuperKEKB is 8 mid 1035 cm-2s-1 – 50 times larger than that of the present KEKB collider. The current Belle detector will also be upgraded to take a full advantage of the high collider luminosity. The new detector, SuperBelle, is designed in such a way that it should perform at least as well as the present Belle spectrometer, despite the substantial increase in beam-induced backgrounds.
Ključne besede: KEKB, SuperKEKB, B mesons, B factories, SuperBelle
Objavljeno: 30.06.2017; Ogledov: 329; Prenosov: 171
.pdf Celotno besedilo (1,04 MB)
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6.
Measurement of D0–D‾0 mixing and search for CP violation in D0 → K+K−,π+π− decays with the full Belle data set
Marko Starič, Jyoti Prakash Biswal, Marko Bračko, Boštjan Golob, Samo Korpar, Peter Križan, Tara Nanut, Rok Pestotnik, Marko Petrič, Eva Ribežl, Samo Stanič, Anže Zupanc, 2016, izvirni znanstveni članek

Opis: We report an improved measurement of $D^0–{\overline{D}}^0$ mixing and a search for $CP$ violation in $D^0$ decays to $CP$ -even final states $K^+K^−$ and $\pi^+\pi^-$. The measurement is based on the final Belle data sample of $976 fb^{−1}$. The results are $y_CP=(1.11±0.22±0.09)%$ and $A_Γ=(−0.03±0.20±0.07)%$, where the first uncertainty is statistical and the second is systematic.
Ključne besede: charm mesons, mixing, CP violation
Objavljeno: 17.07.2017; Ogledov: 299; Prenosov: 178
.pdf Celotno besedilo (577,27 KB)
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7.
First model-independent Dalitz analysis of $B^0 \to D^0K^{\ast 0}$, $D\to K_S^0\pi ^+\pi ^-$ decay
K. 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, izvirni znanstveni članek

Opis: 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 model-independent 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 $B^0 \to \bar {D^0}K^{\ast 0}$.
Ključne besede: CO2, CO3, Cabibbo-Kobayashi-Maskawa quark-mixing matrix, CP violation, experimental particle physics
Objavljeno: 21.07.2017; Ogledov: 328; Prenosov: 57
.pdf Celotno besedilo (555,01 KB)
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8.
High-statistics study of $K^0_S K^0_S$ pair production in two-photon collisions
S. Uehara, Marko Bračko, Boštjan Golob, Jure Klučar, Samo Korpar, Peter Križan, Rok Pestotnik, Marko Petrič, Marko Starič, Luka Šantelj, Anže Zupanc, 2013, izvirni znanstveni članek

Opis: We report a high-statistics 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 center-of-mass energy of the colliding photons, using 972 $^{-1}$ of data collected with the Belle detector at the KEKB asymmetric-energy 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 two-photon 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 CP-violating 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 QCD-based calculations.
Ključne besede: C00, C05, C07, C21, quantum chromodynamics, quark model, particle properties, lepton collider experiments, experimental particle physics
Objavljeno: 21.07.2017; Ogledov: 303; Prenosov: 32
.pdf Celotno besedilo (2,28 MB)
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9.
Measurement of branching fractions for $B \to J/\psi \eta K$ decays and search for a narrow resonance in the $J/\psi \eta$ final state
T. Iwashita, Marko Bračko, Boštjan Golob, Jure Klučar, Samo Korpar, Peter Križan, Rok Pestotnik, Marko Petrič, Marko Starič, Luka Šantelj, Anže Zupanc, 2014, izvirni znanstveni članek

Opis: 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 asymmetric-energy $e^+e^-$ 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.
Ključne besede: C07, C21, particle properties, lepton collider experiments, experimental particle physics
Objavljeno: 21.07.2017; Ogledov: 295; Prenosov: 62
.pdf Celotno besedilo (372,20 KB)
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10.
Primerjava izračunanih in numeričnih rezultatov pri obravnavi molekule vodika
Tibor Mlakar, 2019, diplomsko delo

Opis: V mnogih vejah teoretične kemije kot fizike zastavljene sisteme proučujemo z reševanjem Schrödingerjeve enačbe. Rešitvam te enačbe pravimo valovne funkcije, s katerimi lahko določimo vse bistvene parametre nekega sistema. Oblika členov Schrödingerjeve enačbe se spreminja skupaj z izbiro sistema, načeloma kompleksnejši kot je proučevani sistem zahtevnejše je reševanje omenjene enačbe. V diplomskem delu smo iskali rešitve Schrödingerjeve enačbe za najenostavnejši analitično rešljiv sistem - molekulo vodikovega iona (H2+). Analitične rešitve smo poiskali v okviru teorije molekulskih orbital (MO), ki smo jih opisali z linearno kombinacijo atomskih orbital (“linear combination of atomic orbitals” - LCAO). Rešitve istega problema smo iskali tudi numerično, z računskim programom Gaussian, pri čemer smo za računanje uporabili tako semi-empirične kot ab initio metode. Rezultate vseh izračunov smo primerjali z eksperimentalno izmerjenimi vrednostmi. V drugem delu diplomske naloge smo analitično iskali rešitve Schrödingerjeve enačbe za nekoliko večji sistem – molekulo vodika (H2). Zaradi pomankanja znanja novega sistema ni bilo možno obravnavati do konca. Ugotovili smo, da enostaven analitični račun vodi do vrednosti za ravnovesno razdaljo in vezavno energijo, ki se v okviru 30-40% ujemata z eksperimentalnimi podatki. Pri numeričnih metodah se je izkazalo, da posamezne ab initio metode privedejo do podobnih rezultatov, prav tako tudi posamezne semi-empirične metode. Ugotovili smo, da je ujemanje rezultatov za ravnovesno razdaljo pri vseh numeričnih metodah znotraj 10% od eksprimentalnih vrednosti. Pri energijah je ujemanje nekoliko slabše, so pa dobljene vrednosti še vedno v okviru 20% proč od eksperimentalnih rezultatov. Edina izjema sta bili obe semi-empirični metodi, ki sta za izračunano energijo sistema dali popolnoma neprimerne rezultate.
Ključne besede: Schrödingerjeva enačba, molekula vodikovega iona, teorija molekulskih orbital, računski program Gaussian, ravnovesna razdalja, energija sistema
Objavljeno: 11.09.2019; Ogledov: 209; Prenosov: 25
.pdf Celotno besedilo (43,20 MB)

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