Strangeness Changing Research Articles

Hypothesis of Rolling Bearing Performance Evolvement

Poor information means that characteristic information presented in the subject investigated is incomplete and insufficient, with a small sample and the lack in prior knowledge of probability distributions and trends. For a long time, experiments on the rolling bearing performance concern primarily with statistical evaluation of the fatigue life. With the development of aeronautic and astronautic undertakings, new requirements for the variability of the bearing performance, such as friction, wear, vibration, and temperature rise, are driven. Because the number of characteristic data is small and prior information on probability distributions and trends is poor, statistics has difficulty in assessing the bearing performance. How can the problem be solved There is a phenomenon in Nature, i.e., genetic variations of a species are likely to result in some strange change. Inspired by this, the paper advanced a hypothesis, viz., maybe some genetic variation drive the nonlinearly dynamical evolvement of the information poor process of the bearing performance. To demonstrate this hypothesis, the paper found the variant gene, presented the concept of the poor information equivalence relation, and proposed the method for construction of the information poor space to reveal the new properties of the nonlinearly dynamical evolvement of the modern bearing performance.

‘Strange changes’: Indigenous perspectives of climate change and adaptation in NE Arnhem Land (Australia)

Despite growing global attention to the development of strategies and policy for climate change adaptation, there has been little allowance for input from Indigenous people. In this study we aimed to improve understanding of factors important in integration of Yolngu perspectives in planning adaptation policy in North East Arnhem Land (Australia). We conducted workshops and in-depth interviews in two ‘communities’ to develop insight into Yolngu peoples’ observations and perspectives on climate change, and their ideas and preferences for adaptation. All participants reported observing changes in their ecological landscape, which they attributed to mining, tourism ‘development’, and climate change. ‘ Strange changes’ noticed particularly in the last five years, had caused concern and anxiety among many participants. Despite their concern about ecological changes, participants were primarily worried about other issues affecting their community's general welfare. The results suggest that strategies and policies are needed to strengthen adaptive capacity of communities to mitigate over-arching poverty and well-being issues, as well as respond to changes in climate. Participants believed that major constraints to strengthening adaptive capacity had external origins, at regional, state and federal levels. Examples are poor communication and engagement, top-down institutional processes that allow little Indigenous voice, and lack of recognition of Indigenous culture and practices. Participants’ preferences for strategies to strengthen community adaptive capacity tended to be those that lead towards greater self-sufficiency, independence, empowerment, resilience and close contact with the natural environment. Based on the results, we developed a simple model to highlight main determinants of community vulnerability. A second model highlights components important in facilitating discourse on enhancing community capacity to adapt to climatic and other stressors.

Chiral extrapolation of the strangeness changing scalar Kπ form factor

We perform a chiral extrapolation of lattice data on the scalar Kπ form factor and the ratio of the kaon and pion decay constants within Chiral Perturbation Theory to two loops. We determine the value of the scalar form factor at zero momentum transfer, at the Callan-Treiman point and at its soft kaon analog as well as its slope. Results are in good agreement with their determination from experiment using the standard couplings of quarks to the W boson. The slope is however rather large. A study of the convergence of the chiral expansion is also performed.

Weak vector and axial-vector form factors in the chiral constituent quark model with configuration mixing

The effects of SU(3) symmetry breaking and configuration mixing have been investigated for the weak vector and axial-vector form factors in the chiral constituent quark model (\chi CQM) for the strangeness changing as well as strangeness conserving semi-leptonic octet baryon decays in the nonperturbative regime. The results are in good agreement with existing experimental data and also show improvement over other phenomenological models.

Analyticity constraints on the strangeness changing vector current and applications to τ→Kπντ and τ→Kππντ

We discuss matrix elements of the strangeness changing vector current using their relation, due to analyticity, with πK scattering in the P-wave. We take into account experimental phase-shift measurements in the elastic channel as well as results, obtained by the LASS collaboration, on the details of inelastic scattering, which show the dominance of two quasi-two-body channels at medium energies. The associated form factors are shown to be completely determined, up to one flavor symmetry breaking parameter, imposing boundary conditions at t=0 from chiral and flavor symmetries and at t→∞ from QCD. We apply the results to the τ→Kπντ and τ→Kππντ amplitudes and compare the former to recent high statistics results from B factories.

New results for the production of Λ and Σhyperons in antineutrino scattering from protons

We obtain total and differential cross-sections for the strangeness changing charged current reactions ¯ + p → Λ + L + and ¯ + p → Σ0 + L + , where L is a charged lepton, either an electron, muon or tau. We do this by making use of the standard dipole form factors normally used and of the new form factors recently obtained from recoil proton measurements in electron-proton electromagnetic scattering. We also obtain the contributions of the individual form factors to the total and differential cross-sections for both sets of form factors. We find that the differential and total cross-sections for Λ production change only slightly between the two sets of form factors but that the differential and total cross-sections change substantially for Σ0 production. We discuss the possibility of distinguishing between the two cases for the experiments planned by the MINERν A Collaboration.

Occupation number formalism for arbitrary Nc baryons

A general method is presented for computing matrix elements of quark operators on baryonic states with low strangeness and arbitrary number of colors N c . These results are useful in applications of the large N c expansion to baryons and exotics. As an application we compute the matrix elements of strangeness changing operators contributing to kaon couplings to ground state baryons and pentaquarks, in broken SU ( 3 ) .

The weak production of Λ particles in antineutrino–proton scattering and the contributions of the form factors

In support of proposed experiments which might be carried out by the MINER νA Collaboration and eventually elsewhere, we study the strangeness changing charged current reactions ν ¯ L + p → Λ + L + where L stands for an electron, muon, or tau lepton. We calculate the total and differential cross sections for these reactions from near threshold to several GeV. We also obtain the contributions of the various form factors and interference terms to the total and differential cross sections. The calculation is phenomenologically based and makes use of SU(3) relations to obtain the standard vector current form factors and data from Λ beta decay to obtain the axial current form factor. We also make estimates for the contributions of the pseudoscalar form factor and for the F E and F S form factors to the total and differential cross sections. The latter two are second class current form factors for the corresponding p ↔ n transition and forbidden by G-parity but are not forbidden here. We discuss our results and consider under what circumstances we might extract the various form factors. In particular we wish to test the SU(3) obtained form factors and to test the assumptions made in determining the others over a range of q 2 values.

The weak production of Λ hyperons from lepton-proton scattering

We obtain the differential cross sections for the weak, strangeness changing processes, e − + p → Λ + ν e , μ − + p → Λ + ν μ , and τ − + p → Λ + ν τ as well as cross sections for the processes ν ¯ L + p → Λ + L + , where L stands for either a muon or a tau. We do this for electron energies from threshold to 2.0 GeV, for muon energies from near threshold to 5.0 GeV, for a tau energy of 20.0 GeV, and for muon antineutrino energies from threshold to 1.0 GeV and tau antineutrino energies near threshold. We discuss what might be learned from these reactions and obtain the contributions of the various form factors to these cross sections. We pay particular attention to the interference terms which may represent the only possibility of obtaining the weak magnetism form factor, F M , the pseudoscalar form factor, F P , and the form factor, F E . This latter form factor is forbidden by G-parity in the p ↔ n transition but is in principle permitted in the p ↔ Λ transition and its presence would therefore be of interest. Our calculation is a phenomenological one and makes use of SU(3) relations and Λ beta decay data.

The weak production of Λ particles in muon and tau scattering from protons

We calculate the differential cross sections for the weak strangeness changing processes, μ −+ p→ Λ+ ν μ and τ −+ p→ Λ+ ν τ . We do the muon reaction from near threshold to 5.0 GeV and the tau reaction at 20.0 GeV. This relatively high energy is made necessary by the short lifetime of the tau lepton. We make use of SU(3) relations and experimental data so that the calculation presented is phenomenological in nature. We obtain the contributions from the form factors including interference terms with a view to extracting those parts of the cross section which are suppressed in the corresponding electron induced reaction due to the small size of the electron mass. Finally we discuss what might be learned from these reactions and the conditions necessary for performing these experiments.

The weak production of Λ particles in electron–proton scattering and the contributions of the interference terms

We obtain the contributions of the interference terms to the differential cross section for the weak, strangeness changing, electron scattering process, for incoming electron energies of 194.25 MeV, 2.0 GeV and 10.0 GeV, where the first energy is near the threshold value for the reaction. We are particularly interested in calculating these interference term contributions in order to support the efforts of two proposed experiments for the continuous electron beam accelerator at the Thomas Jefferson National Accelerator Facility. We see that the large interference terms are generally the FAFV and FAFM terms which should be extractable, thereby allowing determinations of FA, FV and FM. In addition, it might be possible to place limits on the FAFE term and hence on FE. This latter contribution is particularly interesting because FE in a proton–neutron transition is normally forbidden by G-parity but is not forbidden in weak Λ production.

The weak electroproduction of [formula omitted] in electron–proton scattering

We obtain differential cross sections for the reaction e −+p→Σ 0+ν e , for incident electron energies from 0.5 GeV to 6.0 GeV. This calculation is phenomenologically based and makes use of SU(3) and SU(2) relations. We obtain contributions of the individual form factors to the differential cross section and show that the vector current form factor dominates in the region of observability. We also obtain reaction rates for a standard set of conditions. Finally we compare this case with that for Λ production and discuss what might be learned from this reaction concerning the structure of the weak, strangeness changing, hadronic current.

TOPOLOGICAL ASPECTS OF CHIRAL ANOMALY, ORIGIN OF MASS AND ELECTROWEAK THEORY

It is here shown that the topological property of a fermion which gives rise to the fermion number and is related to chiral anomaly may be taken to lead to weak interaction gauge bosons when currents are written in chiral form. The gauge bosons attain mass topologically through the generation of internal helicities and thus no Higgs scalar is needed to have spontaneous symmetry breaking. Moreover the group structure SU(2)×U(1) is inbuilt here for electroweak unification. The Weinberg angle gets a physical meaning and strangeness changing neutral lepton current interaction is automatically forbidden. This formalism also suggests that at very high temperature, weak interaction will be of long range in nature.

The reaction e− + p → Λ + ν and the contributions of the individual form factors to the differential cross section

We calculate the differential cross section for the weak, strangeness changing, electron scattering process, e − + p → Λ + ν, for incoming electron energies of 0.5, 1.0, 2.0, 4.0, and 6.0 GeV. We obtain as well contributions of the individual form factors to the differential cross sections. We find that the differential cross sections peak as the maximal scattering angle for the Λ is approached and that the peak height increases as the electron energy is increased. The behavior of the differential cross section near the maximal angle is discussed as is the possibility of observing this reaction in a facility such as TJNAF.

Spin observables in thepn→pΛreaction

The T matrix of the $p\stackrel{\ensuremath{\rightarrow}}{n}p\ensuremath{\Lambda}$ reaction, which is a strangeness changing weak process, is derived. The explicit formulas of the spin observables are given for s-wave $p\ensuremath{\Lambda}$ final states which kinematically corresponds to inverse reaction of the weak nonmesonic decay of $\ensuremath{\Lambda}$ hypernuclei. One can study interferences between amplitudes of the parity-conserving and -violating, spin-singlet and -triplet, and isospin-singlet and -triplet. Most of them are not available in the study of the nonmesonic decay and will be measured in the coming experiment. They clarify the structure of the reaction and constrain strongly theoretical models for the weak hyperon nucleon interaction.

Beauty-conserving strangeness-changing rare semileptonic decays ofB s meson

The beauty-conserving strangeness-changing decays ofBs meson are examined. In the charm sector, charm-conserving strangeness changing (Δc = 0, Δs ≠ 0) decays are Cabibbo suppressed and are governed by the CKM elementVus which is much smaller than the CKM diagonal elementVcs, so may be of little interest. On the other hand, in theb-sector, beauty-conserving strangeness changing (Δb = 0, Δs ≠ 0) decays are CKM allowed as the CKM matrix elementVus governing such decays is much larger thanVbc orVbu which govern respectively theb →c orb →u transitions. The phase space available, however, is too small for the decays considered here. The numerical estimates for the decay widths of two such modes ofBs meson are presented.

Pionic matrix elements in neutrinoless double-βdecay

Physics beyond the standard model of electroweak interactions that violates lepton number will, in general, induce operators involving the quark and lepton fields that violate lepton number. I point out that some matrix elements of particular operators are known. In the limit of exact SU(3) flavor symmetry the operator overline{u} gamma_mu (1-gamma_5)d overline{u} gamma_mu (1-gamma_5)d is part of the ${\bf 27}$ representation responsible for Delta I=3/2 strangeness changing decays in the standard model. At leading order in the chiral expansion there is only one coupling constant that describes the weak interactions of the pseudo-Goldstone bosons induced by the 27 representation. The observed branching fraction for K+ to pi+ pi0 determines this coupling constant. Contributions of the form m_s log m_s are used to estimate SU(3) breaking corrections to the relation between K+ to pi+ pi0 and the pi- to pi+ e- e- interaction.

The strange-quark mass from QCD sum rules: An update

Three different ways of determining the strange quark mass using QCD sum rules are reviewed. First, from a QCD sum rule determination of the up and down quark masses, together with the current algebra ratio m s (m u + m d) . Second and third, from QCD sum rules involving the strangeness changing vector and axial-vector current divergences, respectively. Present results are encompassed in the value: m s (1 GeV) = 150±70 MeV. It is argued that until direct, and precision measurements of the relevant spectral functions become availabel, the above error is not likely to be reduced.

Strangeness changing baryon baryon interaction

The weak nonmesonic decay of Λ hypernuclei gives information on the strangeness changing weak baryon baryon interaction. The parity violation of the process has been studied by observing weak nonmesonic decay of polarized Λ hypernuclei. Study of the inverse process pn → pΛ gives much cleaner information on the process. Recent progress on the experimental study is presented.

Two body weak hadronic decays of charmed baryons and b- baryons

The two body Cabibbo favored hadronic decays of charmed baryons into an octet baryon and a pseudoscalar meson are examined in the SU(3) symmetry scheme and those of b-baryons in pole model. The numerical estimates for decay widths and branching ratios of some of the modes are obtained and are in good agreement with experiment. We also study b- conserving strangeness changing mode of b- baryon decays.