Introduction Comparison between VMAT and IMRT, in terms of plan quality is great topic discussion in literature. Purpose Aim of this work is to assess VMAT dosimetric results compared to IMRT ones on ...prostate site. Materials and methods A comparison was made between IMRT and VMAT plans on the first 30 consecutive patients treated with VMAT moderately hypofractionated radiotherapy: 70.2 Gy/26 fractions of 2.7 Gy. IMRT and VMAT plans were elaborated by TPS Elekta Monaco® using a rabiobiological optimization approach. Plans were compared by evaluating D105% , D95% , D93% , D90% , Dmean and D0.5% for the PTV coverage, while for Organs at Risk (OARs), in addition to Dmean and D0.5% , the % of organ receiving 57, 61, 65.8 and 68.4 Gy (rectum), 57, 61, 65.8 and 68.4 (bladder), 35, 39.5 and 43.9 Gy (femoral heads) were considered of interest. Results Dosimetric analysis shows that PTV coverage is better with VMAT technique and that PTV Dmean is higher than about 1 Gy in VMAT treatments: median value for the PTV Dmean was 70,6 Gy in VMAT technique vs 69,7 Gy in IMRT. Regarding OARs sparing, VMAT technique offers a higher sparing of bladder (of about 5% of volume at 57,61 and 65 Gy) and femoral heads (of about 15% of volume at 30 Gy). Conclusions Respect to IMRT, VMAT offers higher plan quality with a better PTV coverage. Regarding OARs, VMAT offers higher sparing of bladder and femoral heads. Besides, VMAT is able to provide a considerable reduction in treatment time offering a better delivery efficiency.
We present a search for the direct production of a light pseudoscalar a decaying into two photons with the Belle II detector at the SuperKEKB collider. We search for the process e+e−→γa, a→γγ in the ...mass range 0.2<ma<9.7 GeV/c2 using data corresponding to an integrated luminosity of (445±3) pb−1. Light pseudoscalars interacting predominantly with standard model gauge bosons (so-called axionlike particles or ALPs) are frequently postulated in extensions of the standard model. We find no evidence for ALPs and set 95% confidence level upper limits on the coupling strength gaγγ of ALPs to photons at the level of 10−3 GeV−1. The limits are the most restrictive to date for 0.2<ma<1 GeV/c2.
A search for the flavor-changing neutral-current decay B+ →K+$ν\bar{ν}$ is performed at the Belle II experiment at the SuperKEKB asymmetric energy electron-positron collider. The data sample ...corresponds to an integrated luminosity of 63 fb-1 collected at the Υ (4S) resonance and a sample of 9 fb-1 collected at an energy 60 MeV below the resonance. Because the measurable decay signature involves only a single charged kaon, a novel measurement approach is used that exploits not only the properties of the B+ →K+$ν\bar{ν}$ decay, but also the inclusive properties of the other B meson in the Υ(4S) $B\bar{B}$ event, to suppress the background from other B meson decays and light-quark pair production. This inclusive tagging approach offers a higher signal efficiency compared to previous searches. No significant signal is observed. An upper limit on the branching fraction of B+ →K+$ν\bar{ν}$ of 4.1 × 10-5 is set at the 90% confidence level.
Theories beyond the standard model often predict the existence of an additional neutral boson, the Z^{'}. Using data collected by the Belle II experiment during 2018 at the SuperKEKB collider, we ...perform the first searches for the invisible decay of a Z^{'} in the process e^{+}e^{-}→μ^{+}μ^{-}Z^{'} and of a lepton-flavor-violating Z^{'} in e^{+}e^{-}→e^{±}μ^{∓}Z^{'}. We do not find any excess of events and set 90% credibility level upper limits on the cross sections of these processes. We translate the former, in the framework of an L_{μ}-L_{τ} theory, into upper limits on the Z^{'} coupling constant at the level of 5×10^{-2}-1 for M_{Z^{'}}≤6 GeV/c^{2}.
We search for lepton-flavor-violating τ^{-}→e^{-}α and τ^{-}→μ^{-}α decays, where α is an invisible spin-0 boson. The search uses electron-positron collisions at 10.58 GeV center-of-mass energy with ...an integrated luminosity of 62.8 fb^{-1}, produced by the SuperKEKB collider and collected with the Belle II detector. We search for an excess in the lepton-energy spectrum of the known τ^{-}→e^{-}νover ¯_{e}ν_{τ} and τ^{-}→μ^{-}νover ¯_{μ}ν_{τ} decays. We report 95% confidence-level upper limits on the branching-fraction ratio B(τ^{-}→e^{-}α)/B(τ^{-}→e^{-}νover ¯_{e}ν_{τ}) in the range (1.1-9.7)×10^{-3} and on B(τ^{-}→μ^{-}α)/B(τ^{-}→μ^{-}νover ¯_{μ}ν_{τ}) in the range (0.7-12.2)×10^{-3} for α masses between 0 and 1.6 GeV/c^{2}. These results provide the most stringent bounds on invisible boson production from τ decays.
The process e+e−→π+π−2π0γ is investigated by means of the initial-state radiation technique, where a photon is emitted from the incoming electron or positron. Using 454.3 fb−1 of data collected ...around a center-of-mass energy of s=10.58 GeV by the BABAR experiment at SLAC, approximately 150000 signal events are obtained. The corresponding nonradiative cross section is measured with a relative uncertainty of 3.6% in the energy region around 1.5 GeV, surpassing all existing measurements in precision. Using this new result, the channel’s contribution to the leading order hadronic vacuum polarization contribution to the anomalous magnetic moment of the muon is calculated as (gμπ+π−2π0−2)/2=(17.9±0.1stat±0.6syst)×10−10 in the energy range 0.85 GeV<ECM<1.8 GeV. In the same energy range, the impact on the running of the fine-structure constant at the Z0-pole is determined as Δαπ+π−2π0(MZ2)=(4.44±0.02stat±0.14syst)×10−4. Furthermore, intermediate resonances are studied and especially the cross section of the process e+e−→ωπ0→π+π−2π0 is measured.
The Belle II Physics Book Kou, E; Bishara, F; Brod, J ...
Progress of theoretical and experimental physics,
02/2020, Letnik:
2020, Številka:
2
Journal Article
Recenzirano
Odprti dostop
The Belle II Theory Interface Platform (B2TiP) was created as a physics prospects working group of the Belle II collaboration in June 2014. It offered a platform where theorists and experimentalists ...could work together to elucidate the potential impacts of the Belle II program, which includes a wide scope of physics topics: B physics, charm, τ, quarkonium physics, electroweak precision measurements, and dark sector searches.
We present the first measurement of the ratio of branching fractions of inclusive semileptonic $B$-meson decays, $R(X_{e/\mu}) = \mathcal{B}(B\to X \, e \, \nu) / \mathcal{B}(B\to X \, \mu \, \nu)$, ...a precision test of electron-muon universality, using data corresponding to $189\,\mathrm{fb}^{-1}$ from electron-positron collisions collected with the Belle II detector. In events where the partner $B$ meson is fully reconstructed, we use fits to the lepton momentum spectra above $1.3\,\mathrm{GeV}/c$ to obtain $R(X_{e/\mu}) = 1.007 \pm 0.009~(\mathrm{stat}) \pm 0.019~(\mathrm{syst})$, which is the most precise lepton-universality test of its kind and agrees with the standard-model expectation.
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