1. Slow control of the Belle II Aerogel Ring Imaging detectorRok Pestotnik, Karol Adamczyk, Rok Dolenec, Samo Korpar, Peter Križan, Andrej Lozar, Luka Šantelj, Andrej Seljak, Luka Senekovič, 2023, izvirni znanstveni članek Objavljeno v DKUM: 09.05.2024; Ogledov: 145; Prenosov: 15
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2. Exploring the potential of a Cherenkov TOF PET scanner : a simulation studyGašper Razdevšek, Rok Pestotnik, Peter Križan, Samo Korpar, Dania Consuegra Rodríguez, Andrej Seljak, Andrej Studen, Rok Dolenec, 2023, izvirni znanstveni članek Opis: The detection of annihilation photons in positron emission tomography (PET) is based on scintillation light detection, but an interesting alternative is detection based on Cherenkov photons. Dense Cherenkov radiators provide an opportunity for high gamma detection efficiency—due to their high stopping power and photofraction—and excellent coincidence time resolution (CTR). However, because only a few tens of Cherenkov photons follow a gamma interaction in the radiator, the detection efficiency, and the energy resolution of a pure Cherenkov detector are an issue. This work explores gamma detection efficiency and CTR of PbF2-based detectors with different surface treatments and photodetectors covering one, two, or all crystal faces. Following the detector simulation analysis, we investigate the potential performance of a full-size Cherenkov PET scanner and quantitatively compare image quality with a commercial clinical PET scanner. We demonstrate that even though pure Cherenkov scanners have basically no energy resolution, the scatter fraction of around 50% is not prohibitively large, and images comparable to the state-of-the-art clinical PET scanner can be achieved due to improved efficiency and CTR attainable with PbF2.
Ključne besede: Cherenkov TOF PET Scanner
Objavljeno v DKUM: 02.04.2024; Ogledov: 218; Prenosov: 11
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3. LAPPD operation using ToFPETv2 PETSYS ASICAndrej Seljak, Marko Bračko, Rok Dolenec, Peter Križan, Andrej Lozar, Rok Pestotnik, Samo Korpar, 2023, objavljeni znanstveni prispevek na konferenci Opis: Single photon sensitive detectors used in high energy physics are, in some applica-tions, required to cover areas the size of several m2, and more specifically in very strong demand with an ever finer imaging and timing capability for Cherenkov Ring Imaging Detector (RICH) configurations. We are evaluating the Large Area Picosecond Photo-detector (LAPPD) produced by INCOM company, as a possible candidate for future RICH detector upgrades. In this work we perform tests on the second generation device, which is capacitively coupled to a custom designed anode back plane, consisting of various pixels and strips varying in size, that allows for connecting various readout systems such as standard laboratory equipment, as well as the TOFPET2 ASIC from PETsys company. Our aim is to evaluate what can be achieved by merging currently available technology, in order to find directions for future developments adapted for specific uses.
Ključne besede: data acquisition circuits, data acquisition concept, front-end electronics for detector readou, digital electronic circuits
Objavljeno v DKUM: 06.02.2024; Ogledov: 278; Prenosov: 17
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4. Search for ▫$Z^\prime \to \mu^+ \mu^-$▫ in the ▫$L_\mu - L_\tau$▫ gauge-symmetric model at BelleT. Czank, Karol Adamczyk, Jyoti Prakash Biswal, Marko Bračko, Boštjan Golob, Samo Korpar, Peter Križan, Manca Mrvar, Rok Pestotnik, Tomaž Podobnik, Samo Stanič, Marko Starič, Luka Šantelj, 2022, izvirni znanstveni članek Opis: We search for a new gauge boson Z′ that couples only to heavy leptons and their corresponding neutrinos in the process e+e−→Z′(→μ+μ−)μ+μ−, using a 643 fb−1 data sample collected by the Belle experiment at or near the Υ(1S,2S,3S,4S,5S) resonances at the KEKB collider. While previous searches for Z′ performed a data-based estimation of the initial state radiation effect, our search for the Z′ is the first to include effects due to initial state radiation in the signal simulated samples that were used in estimating the detection efficiency. No signal is observed in the Z′ mass range of 0.212–10 GeV/c2, and we set an upper limit on the coupling strength, g′, constraining the possible Z′ contribution to the anomalous magnetic dipole moment of the muon.
Ključne besede: Extensions of gauge sector, leptonic, semileptonic & radiative decays
Objavljeno v DKUM: 25.09.2023; Ogledov: 455; Prenosov: 33
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5. Measurement of the branching fraction and ▫$CP$▫ asymmetry for ▫$B \to \bar{D}^0 \pi$▫ decaysT. Bloomfield, Jyoti Prakash Biswal, Marko Bračko, Samo Korpar, Peter Križan, Rok Pestotnik, Tomaž Podobnik, Marko Starič, Luka Šantelj, 2022, izvirni znanstveni članek Opis: We measure the branching fractions and CP asymmetries for the decays B⁰ → D¯ 0π⁰ and B⁺ → D¯ 0π⁺, using a data sample of 772 × 10⁶ BB¯ pairs collected at the ϒ(4S) resonance with the Belle detector at the KEKB e⁺e− collider. The branching fractions obtained and direct CP asym-metries are B(B⁰ → D¯ 0π⁰)=[2.70 0.06(stat) 0.10(syst)]×10−⁴, B(B⁺ → D¯ 0π⁺)=[4.53 0.02(stat) 0.15(syst)]×10−³, ACP(B⁰ → D¯ 0π⁰)= [+0.42 2.05(stat) 1.22(syst)]%, and ACP(B⁺ → D¯ 0π⁺) = [+0.19 0.36(stat) 0.57(syst)]%. The measurements of B are the most precise to date and are in good agreement with previous results, as is the measurement of ACP(B⁺ → D¯ 0π⁺). The measurement of ACP for B⁰ → D¯ 0π⁰ is the first for this mode, and the value is consistent with Standard Model expectations.
Ključne besede: branching fraction, hadronic decays, particle decays, mesons, CP violation, precision measurements
Objavljeno v DKUM: 17.08.2023; Ogledov: 364; Prenosov: 39
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6. Search for the decay ▫$B_s^0 \to \eta \eta$▫S. Bhuyan, Jyoti Prakash Biswal, Marko Bračko, Boštjan Golob, Samo Korpar, Peter Križan, Rok Pestotnik, Marko Starič, Luka Šantelj, 2022, izvirni znanstveni članek Opis: We report results from a search for the decay B0s→ηη using 121.4 fb−1 of data collected at the Υ(5S) resonance with the Belle detector at the KEKB asymmetric-energy e+e− collider. We do not observe any signal and set an upper limit on the branching fraction of 14.3×10−5 at 90% confidence level. This result represents a significant improvement over the previous most stringent limit.
Objavljeno v DKUM: 17.08.2023; Ogledov: 270; Prenosov: 32
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7. Poznavanje zgodovine juda med slovenskimi judoistiTina Pestotnik, 2022, diplomsko delo Opis: Judo je borilna veščina, ki izvira iz Japonske, danes pa je razširjena po petih celinah in več kot 200 državah. Po podatkih Mednarodne judo zveze se s tem športom ukvarja med 8 in 9 milijonov ljudi. Judo je leta 1882 ustanovil Jigoro Kano. Na začetku je bila borilna veščina zasnovana kot samoobramba in izobraževalni sistem, s katerim bi razvijali fizične, moralne in intelektualne sposobnosti. Poučeval naj bi se v treh oblikah: randori, kate in mondo. V ta šport so bile že od začetka vključene tudi ženske, vendar v omejeni obliki. Zgodovina juda je pomemben del športa in tradicije, zato bi jo kot osnovo moral usvojiti vsak judoist. Poznavanje zgodovinskih dosežkov in dogodkov, ki so privedli do juda, kot ga poznamo danes, je osnova za rast in nadaljnji razvoj tega športa.
Diplomsko delo je sestavljeno iz predstavitve juda, Jigora Kana, začetkov juda, prvih tekmovanj in sodniških pravil, začetka in razvoja juda v Sloveniji, vključevanja žensk in oseb s posebnimi potrebami v judo ter manj poznanih oblik juda – kat. Na koncu so predstavljeni najpomembnejši judoisti in nosilci najvišjih pasov v Sloveniji in svetu. V empričnem delu je na podlagi ankete z vprašalnikom podana interpretacija rezultatov.
Ključne besede: judo, zgodovina juda, Jigoro Kano
Objavljeno v DKUM: 16.02.2023; Ogledov: 9540; Prenosov: 39
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8. Particle identification performance of the prototype aerogel RICH counter for the Belle II experimentS. Iwata, Samo Korpar, Peter Križan, Rok Pestotnik, Luka Šantelj, Andrej Seljak, Elvedin Tahirović, 2016, izvirni znanstveni članek Opis: We have developed a new type of particle identification device, called an aerogel ring imaging Cherenkov (ARICH) counter, for the Belle II experiment. It uses silica aerogel tiles as Cherenkov radiators. For detection of Cherenkov photons, hybrid avalanche photo-detectors (HAPDs) are used. The designed HAPD has a high sensitivity to single photons under a strong magnetic field. We have confirmed that the HAPD provides high efficiency for single-photon detection even after exposure to neutron and $\gamma$-ray radiation that exceeds the levels expected in the 10-year Belle II operation. In order to confirm the basic performance of the ARICH counter system, we carried out a beam test at the using a prototype of the ARICH counter with six HAPD modules. The results are in agreement with our expectations and confirm the suitability of the ARICH counter for the Belle II experiment. Based on the in-beam performance of the device, we expect that the identification efficiency at $3.5\,{\rm GeV}/c$ is 97.4% and 4.9% for pions and kaons, respectively. This paper summarizes the development of the HAPD for the ARICH and the evaluation of the performance of the prototype ARICH counter built with the final design components.
Ključne besede: H14, elementary particle physics, particle detectors, Belle II detector, ring imaging Cherenkov counters, RICH counters
Objavljeno v DKUM: 21.07.2017; Ogledov: 1365; Prenosov: 487
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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 stateT. 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 v DKUM: 21.07.2017; Ogledov: 1540; Prenosov: 236
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10. High-statistics study of $K^0_S K^0_S$ pair production in two-photon collisionsS. 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 v DKUM: 21.07.2017; Ogledov: 1578; Prenosov: 241
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