Punzi-loss Abudinén, F.; Bertemes, M.; Bilokin, S. ...
The European physical journal. C, Particles and fields,
2022/2, Letnik:
82, Številka:
2
Journal Article
Recenzirano
Odprti dostop
We present the novel implementation of a non-differentiable metric approximation and a corresponding loss-scheduling aimed at the search for new particles of unknown mass in high energy physics ...experiments. We call the loss-scheduling, based on the minimisation of a figure-of-merit related function typical of particle physics, a Punzi-loss function, and the neural network that utilises this loss function a Punzi-net. We show that the Punzi-net outperforms standard multivariate analysis techniques and generalises well to mass hypotheses for which it was not trained. This is achieved by training a single classifier that provides a coherent and optimal classification of all signal hypotheses over the whole search space. Our result constitutes a complementary approach to fully differentiable analyses in particle physics. We implemented this work using PyTorch and provide users full access to a public repository containing all the codes and a training example.
Punzi-loss Abudinén, F; Bertemes, M; Bilokin, S ...
European physical journal. C, Particles and fields,
02/2022, Letnik:
82, Številka:
2
Journal Article
Recenzirano
Odprti dostop
We present the novel implementation of a non-differentiable metric approximation and a corresponding loss-scheduling aimed at the search for new particles of unknown mass in high energy physics ...experiments. We call the loss-scheduling, based on the minimisation of a figure-of-merit related function typical of particle physics, a Punzi-loss function, and the neural network that utilises this loss function a Punzi-net. We show that the Punzi-net outperforms standard multivariate analysis techniques and generalises well to mass hypotheses for which it was not trained. This is achieved by training a single classifier that provides a coherent and optimal classification of all signal hypotheses over the whole search space. Our result constitutes a complementary approach to fully differentiable analyses in particle physics. We implemented this work using PyTorch and provide users full access to a public repository containing all the codes and a training example.
We present a new measurement of the Cabibbo-Kobayashi-Maskawa matrix element |Vcb| from B0→D*−ℓ+νℓ decays, reconstructed with the full Belle data set of 711 fb−1 integrated luminosity. Two form ...factor parametrizations, originally conceived by the Caprini-Lellouch-Neubert (CLN) and the Boyd, Grinstein and Lebed (BGL) groups, are used to extract the product F(1)ηEW|Vcb| and the decay form factors, where F(1) is the normalization factor and ηEW is a small electroweak correction. In the CLN parametrization we find F(1)ηEW|Vcb|=(35.06±0.15±0.56)×10−3, ρ2=1.106±0.031±0.007, R1(1)=1.229±0.028±0.009, R2(1)=0.852±0.021±0.006. For the BGL parametrization we obtain F(1)ηEW|Vcb|=(34.93±0.23±0.59)×10−3, which is consistent with the world average when correcting for F(1)ηEW. The branching fraction of B0→D*−ℓ+νℓ is measured to be B(B0→D*−ℓ+νℓ)=(4.90±0.02±0.16)%. We also present a new test of lepton flavor universality violation in semileptonic B decays, B(B0→D*−e+ν)B(B0→D*−μ+ν)=1.01±0.01±0.03. The errors quoted correspond to the statistical and systematic uncertainties, respectively. This is the most precise measurement of F(1)ηEW|Vcb| and form factors to date and the first experimental study of the BGL form factor parametrization in an experimental measurement.
We present the first measurements of absolute branching fractions of Ξc0 decays into Ξ−π+, ΛK−π+, and pK−K−π+ final states. The measurements are made using a dataset comprising (772±11)×106 BB¯ pairs ...collected at the ϒ(4S) resonance with the Belle detector at the KEKB e+e− collider. We first measure the absolute branching fraction for B−→Λ¯c−Ξc0 using a missing-mass technique; the result is B(B−→Λ¯c−Ξc0)=(9.51±2.10±0.88)×10−4. We subsequently measure the product branching fractions B(B−→Λ¯c−Ξc0)B(Ξc0→Ξ−π+), B(B−→Λ¯c−Ξc0)B(Ξc0→ΛK−π+), and B(B−→Λ¯c−Ξc0)B(Ξc0→pK−K−π+) with improved precision. Dividing these product branching fractions by the result for B−→Λ¯c−Ξc0 yields the following branching fractions: B(Ξc0→Ξ−π+)=(1.80±0.50±0.14)%, B(Ξc0→ΛK−π+)=(1.17±0.37±0.09)%, and B(Ξc0→pK−K−π+)=(0.58±0.23±0.05)%. For the above branching fractions, the first uncertainties are statistical and the second are systematic. Our result for B(Ξc0→Ξ−π+) can be combined with Ξc0 branching fractions measured relative to Ξc0→Ξ−π+ to yield other absolute Ξc0 branching fractions.
Using a data sample of 980 fb−1 of e+e− annihilation data taken with the Belle detector operating at the KEKB asymmetric-energy e+e− collider, we report the results of a study of excited Ξc states ...that decay, via the emission of photons and/or charged pions, into Ξc0 or Ξc+ ground state charmed-strange baryons. We present new measurements of the masses of all members of the Ξc′, Ξc(2645), Ξc(2790), Ξc(2815), and Ξc(2980) isodoublets, measurements of the intrinsic widths of those that decay strongly, and evidence of previously unknown transitions.
Using a data sample of 921.9 fb-1 collected with the Belle detector, we study the process of $e^+e^- → D^+_s D_{s1}(2536)^-+c.c.$ via initial-state radiation. We report the first observation of a ...vector charmoniumlike state decaying to $D^+_s D_{s1}(2536)^-+c.c.$ with a significance of $5.9σ$, including systematic uncertainties. The measured mass and width are $(4625.9^{+6.2}_{-6.0}$(stat)$±0.4$(syst)) MeV/$c_2$ and ($49.8^{+13.9}_{-11.5}$(stat)$±4.0$(syst)) MeV, respectively. The product of the $e^+e^- → D^+_s D_{s1}(2536)^-+c.c.$ cross section and the branching fraction of $D_{s1}(2536)^- → \bar{D}^{*0}K^-$ is measured from the $D_s \bar{D}_{s1}(2536)$ threshold to $5.59$ GeV.
We present the first measurements of absolute branching fractions of Ξ_{c}^{0} decays into Ξ^{-}π^{+}, ΛK^{-}π^{+}, and pK^{-}K^{-}π^{+} final states. The measurements are made using a dataset ...comprising (772±11)×10^{6} BBover ¯ pairs collected at the ϒ(4S) resonance with the Belle detector at the KEKB e^{+}e^{-} collider. We first measure the absolute branching fraction for B^{-}→Λover ¯_{c}^{-}Ξ_{c}^{0} using a missing-mass technique; the result is B(B^{-}→Λover ¯_{c}^{-}Ξ_{c}^{0})=(9.51±2.10±0.88)×10^{-4}. We subsequently measure the product branching fractions B(B^{-}→Λover ¯_{c}^{-}Ξ_{c}^{0})B(Ξ_{c}^{0}→Ξ^{-}π^{+}), B(B^{-}→Λover ¯_{c}^{-}Ξ_{c}^{0})B(Ξ_{c}^{0}→ΛK^{-}π^{+}), and B(B^{-}→Λover ¯_{c}^{-}Ξ_{c}^{0})B(Ξ_{c}^{0}→pK^{-}K^{-}π^{+}) with improved precision. Dividing these product branching fractions by the result for B^{-}→Λover ¯_{c}^{-}Ξ_{c}^{0} yields the following branching fractions: B(Ξ_{c}^{0}→Ξ^{-}π^{+})=(1.80±0.50±0.14)%, B(Ξ_{c}^{0}→ΛK^{-}π^{+})=(1.17±0.37±0.09)%, and B(Ξ_{c}^{0}→pK^{-}K^{-}π^{+})=(0.58±0.23±0.05)%. For the above branching fractions, the first uncertainties are statistical and the second are systematic. Our result for B(Ξ_{c}^{0}→Ξ^{-}π^{+}) can be combined with Ξ_{c}^{0} branching fractions measured relative to Ξ_{c}^{0}→Ξ^{-}π^{+} to yield other absolute Ξ_{c}^{0} branching fractions.
We present the results of the first Dalitz plot analysis of the decay D0 → K−π+η. The analysis is performed on a data set corresponding to an integrated luminosity of 953 fb−1 collected by the ...Belle detector at the asymmetric-energy e+e− KEKB collider. The Dalitz plot is well described by a combination of the six resonant decay channels K* ( 892 )0η, K−a0 ( 980 )+, K−a2 ( 1320 )+, K* ( 1410 )0η, K* ( 1680 )−π+ and K2* ( 1980 )−π+, together with Kπ and Kη S-wave components. The decays K* ( 1680 )− → K−η and K2* ( 1980 )− → K−η are observed for the first time. We measure ratio of the branching fractions, ... (B PDG). Using the Dalitz fit result, the ratio ... is measured to be ...; this is much lower than the theoretical expectations ( ≈ 1 ) made under the assumption that K*( 1680 ) is a pure 13D1 state. The product branching fraction ... is determined. In addition, the π η ′ contribution to the a0( 980 )± resonance shape is confirmed with 10.1 σ statistical significance using the three-channel Flatté model. We also measure ... . This is consistent with, and more precise than, the current world average ( 1.02 ± 0.30 ) % , deviates with a significance of more than 3 σ from the theoretical predictions of (0.51–0.92)%. (ProQuest: ... denotes formulae omited.).
We report measurements of isospin asymmetry Δ0− and difference of direct CP asymmetries ΔACP between charged and neutral B→Xsγ decays. This analysis is based on the data sample containing 772×106BB¯ ...pairs that was collected with the Belle detector at the KEKB energy-asymmetric e+e− collider. Using a sum-of-exclusive technique with invariant Xs mass up to 2.8 GeV/c2, we obtain Δ0−=−0.48±1.49(stat)±0.97(syst)±1.15(f+−/f00)% and ΔACP=+3.69±2.65(stat)±0.76(syst)%, where the last uncertainty for Δ0− is due to the uncertainty on the production ratio of B+B− to B0B¯0 in (4S) decays. The measured value of Δ0− is consistent with zero, allowing us to constrain the resolved photon contribution in the B→Xsγ, and improve the branching fraction prediction. The result for ΔACP is consistent with the prediction of the SM. We also measure the direct CP asymmetries for charged and neutral B→Xsγ decays. All the measurements are the most precise to date.
Here, we discuss the first observation of the radiative charm decay D0 → ρ0γ and the first search for CP violation in decays D0 → ρ0γ , φγ , and K ¯ *0 ( 892 ) γ , using a data sample of 943fb-1 ...collected with the Belle detector at the KEKB asymmetric-energy e+e- collider. The branching fraction is measured to be B ( D0 → ρ0γ ) = ( 1.77±0.30±0.07 ) ×10-5 , where the first uncertainty is statistical and the second is systematic. The obtained CP asymmetries A CP ( D0 → ρ0γ ) =+0.056±0.152±0.006 , A CP ( D0 → φγ ) = -0.094±0.066±0.001 , and A CP ( D0 → K ¯ *0γ ) =-0.003±0.020±0.000 are consistent with no CP violation. Furthermore, we present an improved measurement of the branching fractions B ( D0 → φγ ) = ( 2.76±0.19±0.10 ) ×10-5 and B ( D0 → K ¯ *0γ ) = ( 4.66±0.21±0.21 ) ×10-4 .
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