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2005, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
We review genetic programming principles, their application to FOCUS data samples, and use the method to study the doubly Cabibbo suppressed decay D + → K + π + π -relative to its Cabibbo favored counterpart, D + → K -π + π + . We find that this technique is able to improve upon more traditional analysis methods. To our knowledge, this is the first application of the genetic programming technique to High Energy Physics data.
Physics Letters B, 2005
Cabibbo suppressed (CS) and doubly Cabibbo suppressed (DCS) decays are important in helping us understand the dynamics of hadronic decay processes. DCS decays are unique to the charmed hadrons; charm is the only heavy up-type quark that hadronizes. DCS decay rates are ...
Physics Letters B, 2005
We apply a genetic programming technique to search for the doubly Cabibbo suppressed decays Λ + c → pK + π -and D + s → K + K + π -. We normalize these decays to their Cabibbo favored partners and find BR(Λ + c → pK + π -)/BR(Λ + c → pK -π + ) = (0.05 ± 0.26 ± 0.02)% and BR(D + s → K + K + π -)/BR(D + s → K -K + π + ) = (0.52 ± 0.17 ± 0.11)% where the first errors are statistical and the second are systematic. Expressed as 90% confidence levels (CL), we find < 0.46% and < 0.78% respectively. This is the first successful use of genetic programming in a high energy physics data analysis.
Physics Letters B, 2013
A search for CP violation in the phase-space structures of D 0 and D 0 decays to the final states K − K + π − π + and π − π + π + π − is presented. The search is carried out with a data set corresponding to an integrated luminosity of 1.0 fb −1 collected in 2011 by the LHCb experiment in pp collisions at a centre-of-mass energy of 7 TeV. For the K − K + π − π + final state, the four-body phase space is divided into 32 bins, each bin with approximately 1800 decays. The p-value under the hypothesis of no CP violation is 9.1%, and in no bin is a CP asymmetry greater than 6.5% observed. The phase space of the π − π + π + π − final state is partitioned into 128 bins, each bin with approximately 2500 decays. The p-value under the hypothesis of no CP violation is 41%, and in no bin is a CP asymmetry greater than 5.5% observed. All results are consistent with the hypothesis of no CP violation at the current sensitivity.
Journal of High Energy Physics, 2019
A search for CP violation in the Cabibbo-suppressed D 0 → K + K −π+π− decay mode is performed using an amplitude analysis. The measurement uses a sample of pp collisions recorded by the LHCb experiment during 2011 and 2012, corresponding to an integrated luminosity of 3.0 fb−1. The D 0 mesons are reconstructed from semileptonic b-hadron decays into D 0 μ − X final states. The selected sample contains more than 160 000 signal decays, allowing the most precise amplitude modelling of this D 0 decay to date. The obtained amplitude model is used to perform the search for CP violation. The result is compatible with CP symmetry, with a sensitivity ranging from 1% to 15% depending on the amplitude considered.
Engineering Applications of Artificial Intelligence, 2009
The field of high energy physics aims to discover the underlying structure of matter by searching for and studying exotic particles, such as the top quark and Higgs boson, produced in collisions at modern accelerators. Since such accelerators are extraordinarily expensive, extracting maximal information from the resulting data is essential. However, most accelerator events do not produce particles of interest, so making effective measurements requires event selection, in which events producing particles of interest (signal) are separated from events producing other particles (background). This article studies the use of machine learning to aid event selection. First, we apply supervised learning methods, which have succeeded previously in similar tasks. However, they are suboptimal in this case because they assume the selector with the highest classification accuracy will yield the best final analysis; this is not true in practice, as such analyses are more sensitive to some backgrounds than others. Second, we present a new approach that uses stochastic optimization techniques to directly search for selectors that maximize either the precision of top quark mass measurements or sensitivity to the presence of the Higgs boson. Empirical results confirm that stochastically optimized selectors result in substantially better analyses. We also describe a case study in which the best selector is applied to real data from the Fermilab Tevatron accelerator, resulting in the most precise top quark mass measurement of this type to date. Hence, this new approach to event selection has already contributed to our knowledge of the top quark's mass and our understanding of the larger questions upon which it sheds light.
Physical Review D, 2011
A model-independent search for direct CP violation in the Cabibbo suppressed decay D + → K − K + π + in a sample of approximately 370,000 decays is carried out. The data were collected by the LHCb experiment in 2010 and correspond to an integrated luminosity of 35 pb −1 . The normalized Dalitz plot distributions for D + and D − are compared using four different binning schemes that are sensitive to different manifestations of CP violation. No evidence for CP asymmetry is found.
Computer Physics Communications, 2005
We present a novel multivariate classification technique based on Genetic Programming. The technique is distinct from Genetic Algorithms and offers several advantages compared to Neural Networks and Support Vector Machines. The technique optimizes a set of human-readable classifiers with respect to some user-defined performance measure. We calculate the Vapnik-Chervonenkis dimension of this class of learning machines and consider a practical example: the search for the Standard Model Higgs Boson at the LHC. The resulting classifier is very fast to evaluate, human-readable, and easily portable. The software may be downloaded at:
The European Physical Journal C, 2020
A first search for $$CP$$ CP violation in the Cabibbo-suppressed $${{{\varXi }} ^+_{c}} \rightarrow {p} {{K} ^-} {{\pi } ^+} $$ Ξ c + → p K - π + decay is performed using both a binned and an unbinned model-independent technique in the Dalitz plot. The studies are based on a sample of proton-proton collision data, corresponding to an integrated luminosity of $$3.0\,\text {fb} ^{-1} $$ 3.0 fb - 1 , and collected by the LHCb experiment at centre-of-mass energies of 7 and $$8\,\text {TeV} $$ 8 TeV . The data are consistent with the hypothesis of no $$CP$$ CP violation.
Physical Review Letters, 2004
We report a search for CP -violating asymmetry in B 0 → D * ± D ∓ decays. The analysis employs two methods of B 0 reconstruction: full and partial. In the full reconstruction method all daughter particles of the B 0 are required to be detected; the partial reconstruction technique requires a fully reconstructed D − and only a slow pion from the D * + → D 0 π + slow decay. From a fit to the distribution of the time interval corresponding to the distance between two B meson decay points we calculate the CP -violating parameters and find the significance of nonzero CP asymmetry to be 2.7 standard deviations. PACS numbers: 11.30.Er, 12.15.Hh, 13.25.Hw 3 In the Standard Model (SM), CP violation arises from the Kobayashi-Maskawa (KM) phase [1] in the weak interaction quark-mixing matrix. Comparisons between SM expectations and measurements in various modes are important to test the KM model. The
Physical Review D, 2011
A model-independent search for direct CP violation in the Cabibbo suppressed decay D + → K − K + π + in a sample of approximately 370,000 decays is carried out. The data were collected by the LHCb experiment in 2010 and correspond to an integrated luminosity of 35 pb −1 . The normalized Dalitz plot distributions for D + and D − are compared using four different binning schemes that are sensitive to different manifestations of CP violation. No evidence for CP asymmetry is found.
Physics Letters B, 2005
We present an analysis of the decay D 0 → K + π − based on FOCUS data. From a sample of 234 signal events, we find a branching ratio of Γ(D 0 →K + π −) Γ(D 0 →K − π +) = (0.429 + 0.063 − 0.061 ± 0.027)% under the assumptions of no mixing and no CP violation. Allowing for CP violation, we find a branching ratio of (0.429 ± 0.063 ± 0.028)% and a CP asymmetry of 0.18 ± 0.14 ± 0.04. The branching ratio for the case of mixing with no CP violation is (0.381 + 0.167 − 0.163 ± 0.092)%. We also present limits on charm mixing.
Physical Review Letters, 2005
Physical Review D, 2005
We report on a search for the CP asymmetry in the singly Cabibbo-suppressed decays D + → K − K + π + and in the resonant decays D + → φπ + and D + → K * 0 K + based on a data sample of 79.9 fb −1 recorded by the BABAR detector. We use the Cabibbo-favored D + s → K − K + π + branching fraction as normalization in the measurements to reduce systematic uncertainties. The CP asymmetries obtained are ACP (K − K + π ± ) = (1.4 ± 1.0(stat.) ± 0.8(syst.)) × 10 −2 , ACP (φπ ± ) = (0.2 ± 1.5(stat.) ± 0.6(syst.)) × 10 −2 , and ACP (K * 0 K ± ) = (0.9 ± 1.7(stat.) ± 0.7(syst.)) × 10 −2 . The relative branching fraction Γ(D + →K − K + π + ) Γ(D + →K − π + π + ) is also measured and is found to be (10.7 ± 0.1(stat.) ± 0.2(syst.)) × 10 −2 .
Physical Review Letters, 2006
2011
A model-independent search for direct CP violation in the Cabibbo suppressed decay D + → K − K + π + in a sample of approximately 370,000 decays is carried out. The data were collected by the LHCb experiment in 2010 and correspond to an integrated luminosity of 35 pb −1 . The normalized Dalitz plot distributions for D + and D − are compared using four different binning schemes that are sensitive to different manifestations of CP violation. No evidence for CP asymmetry is found.
2011
A model-independent search for direct CP violation in the Cabibbo suppressed decay D + → K − K + π + in a sample of approximately 370,000 decays is carried out. The data were collected by the LHCb experiment in 2010 and correspond to an integrated luminosity of 35 pb −1 . The normalized Dalitz plot distributions for D + and D − are compared using four different binning schemes that are sensitive to different manifestations of CP violation. No evidence for CP asymmetry is found.
Physical Review D, 2011
We search for CP violation in a sample of 20000 Cabibbo-suppressed decays, D + → K + K 0 S π + π − , and 30000 Cabibbo-favored decays, D + s → K + K 0 S π + π − . We use 520 fb −1 of data recorded by the BABAR detector at the PEP-II asymmetric-energy e + e − collider operating at center of mass energies near 10.6 GeV. We search for CP violation in the difference between the T -odd asymmetries obtained using triple product correlations of the D + (D + s ) and D − (D − s ) decays, respectively. The T violation parameter values obtained are AT (D + ) = (−12.0 ± 10.0 stat ± 4.6 syst ) × 10 −3 and AT (D + s ) = (−13.6 ± 7.7 stat ± 3.4 syst ) × 10 −3 , which are consistent with the standard model expectations. PACS numbers: 13.25.Ft, 11.30.Er In the standard model (SM) of particle physics, the violation of the charge-conjugation and parity symmetries (CP ) is introduced by the Kobayashi-Maskawa (KM) phase in the Cabibbo-Kobayashi-Maskawa quark mixing matrix [1]. The KM ansatz has been tested at high precision in K and B decays, where the KM phase contributes to the quark transition amplitude at tree level. However, further experimental efforts are needed in D meson decays, where CP -violating amplitudes are predicted to contribute to the observables at the 10 −3 level [2]. The sensitivity to CP violation in D meson decays reached by the B factories is of the order of 5 × 10 −3 [3-6]. Although this does not represent a measurement of SM CP violation, it provides a constraint on possible effects beyond the SM. New physics models introduce CP violation in D meson decays through tree and one-loop diagrams. While predictions for CP violation in tree diagrams are not different from those in the SM [O(10 −3 )], new physics in loop diagrams may enhance CP violation effects at the order of 10 −2 [7].
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