1,818 research outputs found
The Physics of the B Factories
No full textForeword “The Physics of the B Factories” describes a decade long effort of physicists in the quest for the precise determination of asymmetry — broken symmetry — between particles and anti-particles. We now recognize that the matter we see around us is the residue — one part in a billion — of the matter and antimatter that existed in the early universe, most of which annihilated into the cosmic background radiation that bathes us. But the question remains: how did the baryonic matter-antimatter asymmetry arise? This book describes the work done by some 1000 physicists and engineers from around the globe on two experimental facilities built to test our understanding of this phenomenon, one at the SLAC National Accelerator Laboratory in California, USA, and a second at the KEK Laboratory, Tsukuba, Japan, and what we have learned from them in broadening our understanding of nature. Why is our universe dominated by the matter of which we are made rather than equal parts of matter and antimatter? This question has puzzled physicists for decades. However, this was not the question we addressed when we wrote the paper on CP violation in 1972. Our question was whether we can explain the CP violation observed in the K meson decay within the framework of the renormalizable gauge theory. At that time, Sakharov’s seminal paper was already published, but it did not attract our attention. If we were aware of the paper, we would have been misled into seeking a model satisfying Sakharov’s conditions and our paper might not have appeared. In our paper, we discussed that we need new particles in order to accommodate CP violation into the renormalizable electroweak theory, and proposed the six-quark scheme as one of the possible ways introducing new particles. We thought that the six-quark scheme is very interesting, but it was just a possibility. The situation changed when the tau-lepton was found and it was followed by the discovery of the Upsilon particle. The existence of the third generation became reality. However, it was still uncertain whether the mixing of the six quarks is a real origin of the observed CP violation. Theoretical calculation of CP asymmetries in the neutral K meson system contains uncertainty from strong interaction effects. What settled this problem were the B Factories built at SLAC and KEK. These B Factories are extraordinary in many ways. In order to fulfill the requirements of special experiments, the beam energies of the colliding electron and positron are asymmetric, and the luminosity is unprecedentedly high. It is also remarkable that severe competition between the two laboratories boosted their performance. One of us (M. Kobayashi) has been watching the development at KEK very closely as the director of the Institute of Particle and Nuclear Studies of KEK for a period of time. As witnesses, we appreciate the amazing achievement of those who participated in these projects at both laboratories. The B Factories have contributed a great deal to our understanding of particle physics, as documented in this book. In particular, thanks to the high luminosity far exceeding the design value, experimental groups measured mixing angles precisely and verified that the dominant source of CP violation observed in the laboratory experiments is flavor mixing among the three generations of quarks. Obviously we owe our Nobel Prize to this result. Now we are awaiting the operation of the nextgeneration Super B Factories. In spite of its great success, the Standard Model is not an ultimate theory. For example, it is not thought to be possible for the matter dominance of the universe to be explained by the Standard Model. This means that there will still be unknown particles and unknown interactions. We have a lot of theoretical speculations but experimental means are rather limited. There are great expectations for the Super B Factories to reveal a clue to the world beyond the Standard Model
First observation of B → D ̄_1 (→ D ̄ π+π-) l+ν l and measurement of the B → D ̄(∗) π l+ νl and B → D ̄(∗) π+ π- l+ νl branching fractions with hadronic tagging at Belle
No full textWe report measurements of the ratios of branching fractions for B→D ̄(∗)πl+νl and B→D ̄(∗)π+π-l+νl relative to B→D ̄∗l+νl decays with l=e, μ. These results are obtained from a data sample that contains 772×106BB ̄ pairs collected near the Υ(4S) resonance with the Belle detector at the KEKB asymmetric energy e+e- collider. Fully reconstructing both B mesons in the event, we obtain B(B0→D ̄0π-l+νl)B(B0→D∗-l+νl)=(7.23±0.36±0.14)%, B(B+→D-π+l+νl)B(B+→D ̄∗0l+νl)=(6.78±0.24±0.18)%, B(B0→D ̄∗0π-l+νl)B(B0→D∗-l+νl)=(11.10±0.48±0.23)%, B(B+→D∗-π+l+νl)B(B+→D ̄∗0l+νl)=(9.50±0.33±0.34)%, B(B0→D-π+π-l+νl)B(B0→D∗-l+νl)=(2.91±0.37±0.26)%, B(B+→D ̄0π+π-l+νl)B(B+→D ̄∗0l+νl)=(3.10±0.26±0.22)%, B(B0→D∗-π+π-l+νl)B(B0→D∗-l+νl)=(0.99±0.43±0.20)%, B(B+→D ̄∗0π+π-l+νl)B(B+→D ̄∗0l+νl)=(1.25±0.27±0.15)%, where the uncertainties are statistical and systematic, respectively. These are the most precise measurements of these branching fraction ratios to date. The invariant mass spectra of the Dπ, D∗π, and Dππ systems are studied, and the branching fraction products B(B0→D2∗-l+νl)×B(D2∗-→D ̄0π-)=(0.157±0.015±0.005)%, B(B+→D ̄0∗0l+νl)×B(D ̄0∗0→D-π+)=(0.054±0.022±0.005)%, B(B+→D ̄2∗0l+νl)×B(D ̄2∗0→D-π+)=(0.163±0.011±0.008)%, B(B0→D1-l+νl)×B(D1-→D ̄∗0π-)=(0.306±0.050±0.029)%, B(B0→D1′-l+νl)×B(D1′-→D ̄∗0π-)=(0.206±0.068±0.025)%, B(B0→D2∗-l+νl)×B(D2∗-→D ̄∗0π-)=(0.051±0.040±0.010)%, B(B+→D ̄10l+νl)×B(D ̄10→D∗-π+)=(0.249±0.023±0.015)%, B(B+→D ̄1′0l+νl)×B(D ̄1′0→D∗-π+)=(0.138±0.036±0.009)%, B(B+→D ̄2∗0l+νl)×B(D ̄2∗0→D∗-π+)=(0.137±0.026±0.009)%, B(B0→D1-l+νl)×B(D1-→D-π+π-)=(0.102±0.013±0.009)%, B(B+→D ̄10l+νl)×B(D ̄10→D ̄0π+π-)=(0.105±0.011±0.009)%, are extracted. This is the first observation of the decays B→D ̄1l+νl with D1→Dπ+π-
Cameron, Dugald: transcript of a video interview (28-May-2014)
No full textInterview with Professor Dugald Cameron, conducted by Professor Tilli Tansey and Mr Alan Yabsley, for the History of Modern Biomedicine Research Group, 28 May 2014, in the Glasgow Art Club. Transcribed by Mrs Debra Gee, and edited by Professor Tilli Tansey and Mr Alan Yabsley. The project management was undertaken by Mr Adam Wilkinson. Professor Dugald Cameron OBE FCSD FRSA (b. 1939) was an Industrial Design student at Glasgow School of Art when he first came into contact with Tom Brown in about 1960, and became involved in the design of the first obstetric ultrasound scanners. He went on to become Head of Industrial Design at the Glasgow School of Art in 1970, and Director in 1991.The History of Modern Biomedicine Research Group is funded by the Wellcome Trust, which is a registered charity (no. 210183). The current interview has been funded by the Wellcome Trust Strategic Award entitled “Makers of modern biomedicine: testimonies and legacy” (2012-2017; awarded to Professor Tilli Tansey)
Study of the decays B -�� Ds1(2536)(+) (D)over-bar(()*())
No full textWe report a study of the decays B -> D-s1(2536)+ (D) over bar (()*()), where (D) over bar (()*()) is (D) over bar (0), D- or D*(-), using a sample of 657 x 10(6)B (B) over bar pairs collected at the Y(4S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. The branching fractions of the decays B+ -> D-s1(2536)(+) (D) over bar (0), B-0 -> D-s1(2536)D-+(-) and B-0 -> D-s1(2536)D+*(-) multiplied by that of D-s1(2536)(+) -> (D*K-0(+) + D*K-+(0)) are found to be (3.97 +/- 0.85 +/- 0.56) x 10(-4), (2.75 +/- 0.62 +/- 0.36) x 10(-4) and (5.01 +/- 1.21 +/- 0.70) x 10(-4), respectively. The ratio B(D-s1 -> D*K-0(+))/B(D-s1 -> D*K-+(0)) is measured to be 0.88 +/- 0.24 +/- 0.08
Search for rare decays B+ → Ds (∗)+ η, Ds (∗)+ K ̄ 0, D+η, and D+K0
No full textWe present a study of rare decay modes B+→Ds+h0, B+→Ds∗+h0, and B+→D+h0, where h0 denotes the neutral meson η or K0, using a data sample of (772±10)×106 BB ̄ events produced at the Υ(4S) resonance. The data were collected by the Belle detector operating at the asymmetric-energy KEKB collider. We find no evidence for these decays, so we set upper limits at the 90% confidence level on the branching fractions of B+→Ds+h0, Ds∗+h0, and D+h0 decay modes. Along with these rare decay modes, we report improved measurements of the color-suppressed decay branching fractions B(B ̄0→D0η)=(26.6±1.2±2.1)×10-5 and B(B ̄0→D0K̄0)=(5.6±0.5±0.2)×10-5. The first and second quoted uncertainties are statistical and systematic, respectively
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.
Evidence of time-dependent CP violation in the decay B^{0}→D^{*+}D^{*-}
No full textWe report a measurement of the CP-odd fraction and the time-dependent CP violation in B-0 -> D*+D*- decays, using 657x10(6) BB events collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. We measure a CP-odd fraction of R-perpendicular to=0.125 +/- 0.043(stat)+/- 0.023(syst). From the distributions of the proper-time intervals between a B-0 -> D*+D*- decay and the other B meson in the event, we obtain evidence of CP violation with measured parameters A(D)(*+)D(*-)=0.15 +/- 0.13(stat)+/- 0.04(syst) and SD*+D*-=-0.96 +/- 0.25(stat)(-0.16)(+0.13)(syst).LPH
Study of B-bar 0 →D+h- (h=K/π) decays at Belle
No full textWe present a measurement of the branching fractions of the Cabibbo favored B ̄0→D+π- and the Cabibbo suppressed B ̄0→D+K- decays. We find B(B ̄0→D+π-)=(2.48±0.01±0.09±0.04)×10-3 and B(B ̄0→D+K-)=(2.03±0.05±0.07±0.03)×10-4 decays, where the first uncertainty is statistical, the second is systematic, and the third uncertainty is due to the D+→K-π+π+ branching fraction. The ratio of branching fractions of B ̄0→D+K- and B ̄0→D+π- is measured to be RD=[8.19±0.20(stat)±0.23(syst)]×10-2. These measurements are performed using the full Belle dataset, which corresponds to 772×106BB ̄ pairs and use the Belle II software framework for data analysis
Measurement of Differential Distributions of and Implications on
No full textWe present a measurement of the differential shapes of exclusive ( and ) decays with
hadronic tag-side reconstruction for the full Belle data set of
integrated luminosity. We extract the
Caprini-Lellouch-Neubert (CLN) and Boyd-Grinstein-Lebed (BGL) form factor
parameters and use an external input for the absolute branching fractions to
determine the Cabibbo-Kobayashi-Maskawa matrix element and find
and with the zero-recoil lattice QCD point
. We also perform a study of the impact of
preliminary beyond zero-recoil lattice QCD calculations on the
determinations. Additionally, we present the lepton flavor universality ratio
, the electron and muon
forward-backward asymmetry and their difference , and the electron and muon longitudinal polarization fraction and
their difference . The
uncertainties quoted correspond to the statistical and systematic
uncertainties, respectively
Measurement of the branching fraction and CP asymmetry for B → D ̄0 π decays
No full textWe 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 (4S) resonance with the Belle detector at the KEKB e+e- collider. The branching fractions obtained and direct CP asymmetries 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
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