B-flavor tagging at Belle II Akopov, N.; Banerjee, Sw; Bauer, M. ...
The European physical journal. C, Particles and fields,
04/2022, Letnik:
82, Številka:
4
Journal Article
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Odprti dostop
We report on new flavor tagging algorithms developed to determine the quark-flavor content of bottom (
) mesons at Belle II. The algorithms provide essential inputs for measurements of quark-flavor ...mixing and charge-parity violation. We validate and evaluate the performance of the algorithms using hadronic
decays with flavor-specific final states reconstructed in a data set corresponding to an integrated luminosity of 62.8 fb
-
1
, collected at the
resonance with the Belle II detector at the SuperKEKB collider. We measure the total effective tagging efficiency to be
ε
eff
=
(
30.0
±
1.2
(
stat
)
±
0.4
(
syst
)
)
%
for a category-based algorithm and
ε
eff
=
(
28.8
±
1.2
(
stat
)
±
0.4
(
syst
)
)
%
for a deep-learning-based algorithm.
The Belle II experiment at the SuperKEKB electron–positron collider aims to collect an unprecedented data set of 50ab−1 to study CP-violation in the B-meson system and to search for Physics beyond ...the Standard Model. SuperKEKB is already the world’s highest-luminosity collider. In order to collect the planned data set within approximately one decade, the target is to reach a peak luminosity of 6 × 1035cm−2s−1 by further increasing the beam currents and reducing the beam size at the interaction point by squeezing the betatron function down to βy∗=0.3mm. To ensure detector longevity and maintain good reconstruction performance, beam backgrounds must remain well controlled. We report on current background rates in Belle II and compare these against simulation. We find that a number of recent refinements have significantly improved the background simulation accuracy. Finally, we estimate the safety margins going forward. We predict that backgrounds should remain high but acceptable until a luminosity of at least 2.8 × 1035cm−2s−1 is reached for βy∗=0.6mm. At this point, the most vulnerable Belle II detectors, the Time-of-Propagation (TOP) particle identification system and the Central Drift Chamber (CDC), have predicted background hit rates from single-beam and luminosity backgrounds that add up to approximately half of the maximum acceptable rates.
A
bstract
We measure
CP
asymmetries and branching-fraction ratios for
B
±
→ DK
±
and
Dπ
±
decays with
D →
$$ {K}_{\textrm{S}}^0 $$
K
S
0
K
±
π
∓
, where
D
is a superposition of
D
0
and
$$ ...\overline{D} $$
D
¯
0
. We use the full data set of the Belle experiment, containing 772
×
10
6
$$ B\overline{B} $$
B
B
¯
pairs, and data from the Belle II experiment, containing 387 × 10
6
$$ B\overline{B} $$
B
B
¯
pairs, both collected in electron-positron collisions at the Υ(4
S
) resonance. Our results provide model-independent information on the unitarity triangle angle
ϕ
3
.
From April to July 2018, a data sample at the peak energy of the resonance was collected with the Belle II detector at the SuperKEKB electron-positron collider. This is the first data sample of the ...Belle II experiment. Using Bhabha and digamma events, we measure the integrated luminosity of the data sample to be ( , where the first uncertainty is statistical and the second is systematic. This work provides a basis for future luminosity measurements at Belle II.
The Belle II experiment at the SuperKEKB electron-positron collider aims to collect an unprecedented data set of \(50~{\rm ab}^{-1}\) to study \(CP\)-violation in the \(B\)-meson system and to search ...for Physics beyond the Standard Model. SuperKEKB is already the world's highest-luminosity collider. In order to collect the planned data set within approximately one decade, the target is to reach a peak luminosity of \(\rm 6 \times 10^{35}~cm^{-2}s^{-1}\) by further increasing the beam currents and reducing the beam size at the interaction point by squeezing the betatron function down to \(\beta^{*}_{\rm y}=\rm 0.3~mm\). To ensure detector longevity and maintain good reconstruction performance, beam backgrounds must remain well controlled. We report on current background rates in Belle II and compare these against simulation. We find that a number of recent refinements have significantly improved the background simulation accuracy. Finally, we estimate the safety margins going forward. We predict that backgrounds should remain high but acceptable until a luminosity of at least \(\rm 2.8 \times 10^{35}~cm^{-2}s^{-1}\) is reached for \(\beta^{*}_{\rm y}=\rm 0.6~mm\). At this point, the most vulnerable Belle II detectors, the Time-of-Propagation (TOP) particle identification system and the Central Drift Chamber (CDC), have predicted background hit rates from single-beam and luminosity backgrounds that add up to approximately half of the maximum acceptable rates.
The discovery of scintillation in the blue regime from polyethylene naphthalate (PEN), a commonly used high-performance industrial polyester plastic, has sparked considerable interest from the ...physics community as a new type of plastic scintillator material. This observation in addition to its good mechanical and radiopurity properties makes PEN an attractive candidate as an active structure scintillator for low-background physics experiments. This paper reports on investigations of its potential in terms of production tests of custom made tiles and various scintillation light output measurements. These investigations substantiate the high potential of usage of PEN in low-background experiments.
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