44,910 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
Evidence for the decay B0→J/ψω and measurement of the relative branching fractions of meson decays to J/ψη and J/ψη′
No full textFirst evidence of the B 0 → J / ψ ω decay is found and the B s 0 → J / ψ η and B s 0 → J / ψ η ′ decays are studied using a dataset corresponding to an integrated luminosity of 1.0 fb -1 collected by the LHCb experiment in proton-proton collisions at a centre-of-mass energy of sqrt(s) = 7 TeV. The branching fractions of these decays are measured relative to that of the B 0 → J / ψ ρ 0 decay:frac(B (B 0 → J / ψ ω), B (B 0 → J / ψ ρ 0)) = 0.89 ± 0.19 (stat) - 0.13 + 0.07 (syst),frac(B (B s 0 → J / ψ η), B (B 0 → J / ψ ρ 0)) = 14.0 ± 1.2 (stat) - 1.5 + 1.1 (syst) - 1.0 + 1.1 (frac(f d, f s)),frac(B (B s 0 → J / ψ η ′), B (B 0 → J / ψ ρ 0)) = 12.7 ± 1.1 (stat) - 1.3 + 0.5 (syst) - 0.9 + 1.0 (frac(f d, f s)), where the last uncertainty is due to the knowledge of f d / f s, the ratio of b-quark hadronization factors that accounts for the different production rate of B 0 and B s 0 mesons. The ratio of the branching fractions of B s 0 → J / ψ η ′ and B s 0 → J / ψ η decays is measured to befrac(B (B s 0 → J / ψ η ′), B (B s 0 → J / ψ η)) = 0.90 ± 0.09 (stat) - 0.02 + 0.06 (syst)
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Measurement of the B0–B0 oscillation frequency Δmd with the decays B0→D−π+ and B0→ J/ψK∗0
No full textThe B
0
–B
0
oscillation frequency Δmd is measured by the LHCb experiment using a dataset corresponding
to an integrated luminosity of 1.0 fb−1
of proton–proton collisions at √
s = 7 TeV, and is found to be
Δmd
=0.5156±0.0051 (stat.)±0.0033 (syst.) ps−1
. The measurement is based on results from analyses
of the decays B
0
→ D
−π
+ (D
−
→ K
+π
−π
−) and B
0
→ J/ψK
∗0
(J/ψ →μ
+μ
−,K
∗0
→ K
+π
−) and
their charge conjugated modes
Measurement of the ratio of branching fractions B(B0→K∗0γ )/B(B0s→φγ ) and the directCP asymmetry inB 0→K∗0γ
No full textThe ratio of branching fractions of the radiative B decays B0→K⁎0γ and B0s→ϕγ has been measured using an integrated luminosity of 1.0 fb−1 of pp collision data collected by the LHCb experiment at a centre-of-mass energy of s√=7TeV. The value obtained is
B(B0→K⁎0γ)B(B0s→ϕγ)=1.23±0.06(stat.)±0.04(syst.)±0.10(fs/fd),
where the first uncertainty is statistical, the second is the experimental systematic uncertainty and the third is associated with the ratio of fragmentation fractions fs/fd. Using the world average value for B(B0→K⁎0γ), the branching fraction B(B0s→ϕγ) is measured to be (3.5±0.4)×10−5.
The direct CP asymmetry in B0→K⁎0γ decays has also been measured with the same data and found to be
ACP(B0→K⁎0γ)=(0.8±1.7(stat.)±0.9(syst.))%.
Both measurements are the most precise to date and are in agreement with the previous experimental results and theoretical expectations
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)
Measurement of CP observables in B-+/- -> D(*)K-+/- and B-+/- -> D(*)pi(+/-) decays
No full textMeasurements of CP observables in B-+/- -> D(*)K-+/- and B-+/- -> D(*)pi(+/-) decays are presented, where D(*) indicates a neutral Dor D* meson that is an admixture of D(*)(0) and (D) over bar(*)(0) states. Decays of the D* meson to the D pi(0)and D gamma final states are partially reconstructed without inclusion of the neutral pion or photon, resulting in distinctive shapes in the Bcandidate invariant mass distribution. Decays of the D meson are fully reconstructed in the K-+/-pi(-/+), K+K- and pi(+)pi(-) final states. The analysis uses a sample of charged Bmesons produced in ppcollisions collected by the LHCb experiment, corresponding to an integrated luminosity of 2.0, 1.0 and 2.0fb- 1taken at centre- of- mass energies of root s = 7, 8 and 13 TeV, respectively. The study of B-perpendicular to -> D*K-perpendicular to and B-perpendicular to -> D*pi(perpendicular to) decays using a partial reconstruction method is the first of its kind, while the measurement of B-+/- -> DK +/- and B-+/- -> D pi(+/-) decays is an update of previous LHCb measurements. The B-+/- -> DK +/- results are the most precise to date. (c) 2017 The Author. Published by Elsevier B. V
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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
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