511 research outputs found
Studium procesů s účastí kvarku b v experimentu Belle
No full textTitle: Study of b-quark processes in the Belle experiment Author: Daniel Červenkov Department: Institute of Particle and Nuclear Physics Supervisor: Zdeněk Doležal Co-Supervisor: Karim Trabelsi Abstract: A study regarding the plausability of using the B0 → D∗ ρ± decay channel and the data set of the Belle experiment to measure sin(2φ1+φ3) has been carried out. Two fitters have been created. A time-independent one, which ex- hibits high stability and reports gratifying fit uncertainties, and a time-dependent one. During the testing of the latter we have discovered an EvtGen flaw and pro- posed a temporary workaround. Nevertheless, the time-dependent fitter fails to recover the correct values. More work will be needed to reach conclusive results. Keywords: B meson, CP violation, angular analysis, time-dependent, fitte
Simulation of noise in the Belle II strip vertex detector
No full textTitle: Simulation of noise in the Belle II strip vertex detector Author: Zuzana Gruberová Institute: Institute of Particle and Nuclear Physics Supervisor: RNDr. Peter Kvasnička, Institute of Particle and Nuclear Physics Abstract: This bachelor thesis describes the development of strip noise simulation for the Belle II strip vertex detector (SVD). The overview part of the thesis describes the Belle II experiment and its detector system. The next part summarizes the basic princi- ples of semiconductor detectors with a focus on electronic noise. This section is followed by a more detailed description of Belle II SVD, its noise characteristics and simulation methods. The methods part introduces basic concepts of noise simulation using ma- chine learning methods, in particular, artificial neural networks. The experimental part describes the development and implementation of a production noise generator, and dis- cusses the performance, precision, and alternative solutions. Keywords: particle physics, Belle II, strip detector, noise, simulation, neural network
Simulace šumu ve stripovém vrcholovém detektoru Belle II
No full textNázev práce: Simulace šumu ve stripovém vrcholovém detektoru Belle II Autor: Zuzana Gruberová Ústav: Ústav částicové a jaderné fyziky Vedoucí bakalářské práce: RNDr. Peter Kvasnička, Ústav částicové a jaderné fyziky Abstrakt: Tato bakalářská práce se zabývá vývojem simulace šumu ve stripovém vr- cholovém detektoru (SVD) pro experiment Belle II. Úvodní část popisuje experiment Belle II a jeho systém detektorů. Další část shrnuje základní principy polovodičových detektorů se zaměřeném na elektronický šum. Tato sekce je následována detailnějším popisem Belle II SVD, charakterizací jeho šumu a simulačních metod. Metodická část představuje základní koncepty simulace šumu pomocí strojového učení, konkrétně umělé neuronové sítě. Experimentální část popisuje vývoj a implementaci produkčního generá- toru šumu a diskutuje jeho výsledky, přesnost a alternativní řešení. Klíčová slova: částicová fyzika, Belle II, stripový detektor, šum, simulace, neurální síť 1Title: Simulation of noise in the Belle II strip vertex detector Author: Zuzana Gruberová Institute: Institute of Particle and Nuclear Physics Supervisor: RNDr. Peter Kvasnička, Institute of Particle and Nuclear Physics Abstract: This bachelor thesis describes the development of strip noise simulation for the Belle II strip vertex detector (SVD). The overview part of the thesis describes the Belle II experiment and its detector system. The next part summarizes the basic princi- ples of semiconductor detectors with a focus on electronic noise. This section is followed by a more detailed description of Belle II SVD, its noise characteristics and simulation methods. The methods part introduces basic concepts of noise simulation using ma- chine learning methods, in particular, artificial neural networks. The experimental part describes the development and implementation of a production noise generator, and dis- cusses the performance, precision, and alternative solutions. Keywords: particle physics, Belle II, strip detector, noise, simulation, neural network 1Institute of Particle and Nuclear PhysicsÚstav částicové a jaderné fyzikyMatematicko-fyzikální fakultaFaculty of Mathematics and Physic
Studium rozpadů B-mezonů v experimentu Belle
No full textV této práci se zaměřujeme na studium rozpadu B0 mezonu na mezony D∗ s a ρ. Práce vysvětluje metody a přístupy k analýze dat na takzvaných B-továrnách, jakou je urychlovač KEKB. Cíl této teze je vypočítat větvící poměr zmíněného rozpadu, upřesnit již změřený větvící poměr změřený na experimentu BaBar pomocí dat získaných z experimentu s vyšší integrovanou luminositou. Výhledy této teze nejsou jenom v rozšíření našeho poznání větvících poměrů rozpadů B0 mezonu, ale také jako první krok vedoucí k rozšíření poznání narušení CP symetrie v Standardním modelu měřením úhlů Unitárního trojůhelníku. 1In the thesis we study the decay of B0 meson to D∗ s and ρ mesons. The thesis explains the methods and approaches to data analysis in so-called B-factories, simmilar to the KEKB accelerator. The aim of this thesis is to calculate the branching fraction of this decay to further improve the previously measured branching ratio at BaBar experiment with additional data gained from an ex- periment with higher integrated luminosity. This thesis's prospect is not only broadening our knowledge of branching fractions of B0 meson decays, but also it is a starting point for further analysis with the goal of broadening our knowl- edge of CP symmetry violation in the Standard Model by measuring angles of the Unitary Triangle. 1Ústav částicové a jaderné fyzikyInstitute of Particle and Nuclear PhysicsMatematicko-fyzikální fakultaFaculty of Mathematics and Physic
Studium CP narušení na experimentu Belle
No full textWe present a first measurement of time-dependent CP-violation in B0 → D∗∓ ρ± , where D∗∓ → D0 π. The analysis was performed using the final Belle dataset containing 772 × 106 B ¯B pairs collected at the KEKB e+ e− collider. Three D0 decay modes are analyzed, K∓ π± , K∓ π± π0 , and K∓ π± π∓ π± . Since the studied decay is a scalar → vector vector decay, three helicity configurations are present. Exploiting the helicity configura- tions via angular analysis, the time-dependent CP-violation parameters encoding 2ϕ1 +ϕ3 are obtained from the fit. 1Předkládáme první měření časově závislého CP narušení v rozpadu B0 → D∗∓ ρ± , kde D∗∓ → D0 π. Analýza byla provedena s použitím finálního Belle datasetu obsahujícího 772×106 B ¯B párů. Tento vzorek byl získán na e+ e− urychlovači KEKB. Studovali jsme tři rozpadové módy D0 : K∓ π± , K∓ π± π0 a K∓ π± π∓ π± . Jelikož jde o rozpad typu skalár → vektor vektor, obsahuje tři helicitní konfigurace. Úhlová analýza nám poskytla přístup k těmto konfiguracím, což nám umožnilo provést časově závislý fit parametrů CP narušení, které obsahují informaci o 2ϕ1 + ϕ3. 1Ústav částicové a jaderné fyzikyInstitute of Particle and Nuclear PhysicsFaculty of Mathematics and PhysicsMatematicko-fyzikální fakult
Study of CP-violation at the Belle experiment
No full textWe present a first measurement of time-dependent CP-violation in B0 → D∗∓ ρ± , where D∗∓ → D0 π. The analysis was performed using the final Belle dataset containing 772 × 106 B ¯B pairs collected at the KEKB e+ e− collider. Three D0 decay modes are analyzed, K∓ π± , K∓ π± π0 , and K∓ π± π∓ π± . Since the studied decay is a scalar → vector vector decay, three helicity configurations are present. Exploiting the helicity configura- tions via angular analysis, the time-dependent CP-violation parameters encoding 2ϕ1 +ϕ3 are obtained from the fit.
Observation of an alternative candidate in
No full textWe perform a full amplitude analysis of the process , where refers to either or . A new charmoniumlike state that decays to is observed with a significance of . Its mass is () MeV/ and width is () MeV. The hypothesis is favored over the hypothesis at the level of . The analysis is based on the 980 data sample collected by the Belle detector at the asymmetric-energy collider KEKB
First observation of and measurement of the and branching fractions with hadronic tagging at Belle
No full textWe report measurements of the ratios of branching fractions for and relative to decays with . These results are
obtained from a data sample that contains pairs
collected near the resonance with the Belle detector at the KEKB
asymmetric energy collider. Fully reconstructing both mesons in
the event, we obtain \begin{align*} \frac{B(B^0 \to
\bar{D}^0\pi^-\ell^+\nu_\ell)}{B(B^0 \to D^{*-}\ell^+\nu_\ell)} &=
(7.24\pm0.36\pm0.12)\%\ ,\\ \frac{B(B^+ \to D^-\pi^+\ell^+\nu_\ell)}{B(B^+ \to
\bar{D}^{*0}\ell^+\nu_\ell)} &= (6.78\pm0.24\pm0.15)\%\ ,\\ \frac{B(B^0 \to
\bar{D}^{*0}\pi^-\ell^+\nu_\ell)}{B(B^0 \to D^{*-}\ell^+\nu_\ell)} &=
(11.10\pm0.48\pm0.20)\%\ ,\\ \frac{B(B^+ \to D^{*-}\pi^+\ell^+\nu_\ell)}{B(B^+
\to \bar{D}^{*0}\ell^+\nu_\ell)} &= (9.50\pm0.33\pm0.27)\%\ ,\\ \frac{B(B^0 \to
D^-\pi^+\pi^-\ell^+\nu_\ell)}{B(B^0 \to D^{*-}\ell^+\nu_\ell)} &=
(2.91\pm0.37\pm0.25)\%\ ,\\ \frac{B(B^+ \to
\bar{D}^0\pi^+\pi^-\ell^+\nu_\ell)}{B(B^+ \to \bar{D}^{*0}\ell^+\nu_\ell)} &=
(3.10\pm0.26\pm0.21)\%\ ,\\ \frac{B(B^0 \to
D^{*-}\pi^+\pi^-\ell^+\nu_\ell)}{B(B^0 \to D^{*-}\ell^+\nu_\ell)} &=
(1.03\pm0.43\pm0.18)\%\ ,\\ \frac{B(B^+ \to
\bar{D}^{*0}\pi^+\pi^-\ell^+\nu_\ell)}{B(B^+ \to \bar{D}^{*0}\ell^+\nu_\ell)}
&= (1.25\pm0.27\pm0.15)\%\ , \end{align*} where the uncertainties are
statistical and systematic, respectively. The invariant mass spectra of the
, , and systems are studied. Branching fraction
products are extracted, among them the first observations of and .Comment: submitted to Phys. Rev.
Study of the lineshape of using decays to
No full textWe present a study of the lineshape in the decay using a data sample of
pairs collected at the resonance with the Belle
detector at the KEKB asymmetric-energy collider. The peak near the
threshold in the invariant mass spectrum is fitted
using a relativistic Breit-Wigner lineshape. We determine the mass and width
parameters to be and , respectively. The branching fraction is found to be
. The signal from decays is observed for the first
time with significance, and the ratio of branching fractions
between charged and neutral decays is measured to be . The peak is also studied using a Flatt\'{e}
lineshape. We determine the lower limit on the coupling
constant to be at 95% credibility in the parameter region where the
ratio of to the mass difference from the threshold
is equal to , as measured by LHCb.Comment: submitted to Phys. Rev
Search for CP violation in the D⁺→π⁺π0 decay at Belle
No full textWe search for CP violation in the charged charm meson decay D⁺→π⁺π0, based on a data sample corresponding to an integrated luminosity of 921 fb⁻1 collected by the Belle experiment at the KEKB e⁺e⁻ asymmetric-energy collider. The measured CP-violating asymmetry is [+2031 ± 1.24(stat) ± 0.23(syst)]%, which is consistent with the standard model prediction and has a significantly improved precision compared to previous results
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