1,725,334 research outputs found
Natural NMSSM Higgs bosons
Full text linkWe study the phenomenology of Higgs bosons close to 126 GeV within the scale invariant unconstrained Next-to-Minimal Supersymmetric Standard Model (NMSSM), focusing on the regions of parameter space favoured by low fine-tuning considerations, namely stop masses of order 400 GeV to 1 TeV and an effective ? parameter between 100–200 GeV, with large (but perturbative) ? and low View the MathML sourcetan?=2–4. We perform scans over the above parameter space, focusing on the observable Higgs cross sections into ??, WW, ZZ, bb, ?? final states, and study the correlations between these observables. We show that the ?? signal strength may be enhanced up to a factor of about two not only due to the effect of singlet–doublet mixing, which occurs more often when the 126 GeV Higgs boson is the next-to-lightest CP-even one, but also due to light stops (and to a lesser extent light chargino and charged Higgs loops). There may be also smaller enhancements in the Higgs decay channels into WW, ZZ, correlated with the ?? enhancement. However there is no such correlation observed involving the Higgs decay channels into bb, ??. The requirement of having perturbative couplings up to the GUT scale favours the interpretation of the 126 GeV Higgs boson as being the second lightest NMSSM CP-even state, which can decay into pairs of lighter neutralinos, CP-even or CP-odd Higgs bosons, leading to characteristic signatures of the NMSSM. In a non-negligible part of the parameter range the increase in the ?? rate is due to the superposition of rates from nearly degenerate Higgs bosons. Resolving these Higgs bosons would rule out the Standard Model, and provide evidence for the NMSSM
A Simple parameterization of matter effects on neutrino oscillations
No full textWe present simple analytical approximations to matter-effect corrected effective neutrino mixing-angles and effective mass-squared-differences. The expressions clarify the dependence of oscillation probabilities in matter to the mixing angles and mass-squared-differences in vacuum, and are useful for analyzing long-baseline neutrino oscillation experiments.archiveprefix: arXiv primaryclass: hep-ph reportnumber: OCHA-PP-252, YITP-05-52, VPI-IPPAP-06-01 slaccitation: %%CITATION = HEP-PH/0602115;%%false (Extension publication?
Reply to: ''Improved Determination of the CKM Angle alpha from B -> pipi decays''
No full textIn reply to hep-ph/0701204 we demonstrate why the arguments made therein do not address the criticism exposed in hep-ph/0607246 on the fundamental shortcomings of the Bayesian approach when it comes to the extraction of parameters of Nature from experimental data. As for the isospin analysis and the CKM angle alpha it is shown that the use of uniform priors for the observed quantities in the Explicit Solution parametrization is equivalent to a frequentist construction resulting from a change of variables, and thus relies neither on prior PDFs nor on Bayes' theorem. This procedure provides in this particular case results that are similar to the Confidence Level approach, but the treatment of mirror solutions remains incorrect and it is far from being general. In a second part it is shown that important differences subsist between the Bayesian and frequentist approaches, when following the proposal of hep-ph/0701204 and inserting additional information on the hadronic amplitudes beyond isospin invariance. In particular the frequentist result preserves the exact degeneracy that is expected from the remaining symmetries of the problem while the Bayesian procedure does not. Moreover, in the Bayesian approach reducing inference to the 68% or 95% credible interval is a misconception of the meaning of the posterior PDF, which in turn implies that the significant dependence of the latter to the chosen parametrization cannot be viewed as a minor effect, contrary to the claim in hep-ph/0701204.In reply to hep-ph/0701204 we demonstrate why the arguments made therein do not address the criticism exposed in hep-ph/0607246 on the fundamental shortcomings of the Bayesian approach when it comes to the extraction of parameters of Nature from experimental data. As for the isospin analysis and the CKM angle alpha it is shown that the use of uniform priors for the observed quantities in the Explicit Solution parametrization is equivalent to a frequentist construction resulting from a change of variables, and thus relies neither on prior PDFs nor on Bayes' theorem. This procedure provides in this particular case results that are similar to the Confidence Level approach, but the treatment of mirror solutions remains incorrect and it is far from being general. In a second part it is shown that important differences subsist between the Bayesian and frequentist approaches, when following the proposal of hep-ph/0701204 and inserting additional information on the hadronic amplitudes beyond isospin invariance. In particular the frequentist result preserves the exact degeneracy that is expected from the remaining symmetries of the problem while the Bayesian procedure does not. Moreover, in the Bayesian approach reducing inference to the 68% or 95% credible interval is a misconception of the meaning of the posterior PDF, which in turn implies that the significant dependence of the latter to the chosen parametrization cannot be viewed as a minor effect, contrary to the claim in hep-ph/0701204.In reply to hep-ph/0701204 we demonstrate why the arguments made therein do not address the criticism exposed in hep-ph/0607246 on the fundamental shortcomings of the Bayesian approach when it comes to the extraction of parameters of Nature from experimental data. As for the isospin analysis and the CKM angle alpha it is shown that the use of uniform priors for the observed quantities in the Explicit Solution parametrization is equivalent to a frequentist construction resulting from a change of variables, and thus relies neither on prior PDFs nor on Bayes' theorem. This procedure provides in this particular case results that are similar to the Confidence Level approach, but the treatment of mirror solutions remains incorrect and it is far from being general. In a second part it is shown that important differences subsist between the Bayesian and frequentist approaches, when following the proposal of hep-ph/0701204 and inserting additional information on the hadronic amplitudes beyond isospin invariance. In particular the frequentist result preserves the exact degeneracy that is expected from the remaining symmetries of the problem while the Bayesian procedure does not. Moreover, in the Bayesian approach reducing inference to the 68% or 95% credible interval is a misconception of the meaning of the posterior PDF, which in turn implies that the significant dependence of the latter to the chosen parametrization cannot be viewed as a minor effect, contrary to the claim in hep-ph/0701204.In reply to hep-ph/0701204 we demonstrate why the arguments made therein do not address the criticism exposed in hep-ph/0607246 on the fundamental shortcomings of the Bayesian approach when it comes to the extraction of parameters of Nature from experimental data. As for the isospin analysis and the CKM angle alpha it is shown that the use of uniform priors for the observed quantities in the Explicit Solution parametrization is equivalent to a frequentist construction resulting from a change of variables, and thus relies neither on prior PDFs nor on Bayes' theorem. This procedure provides in this particular case results that are similar to the Confidence Level approach, but the treatment of mirror solutions remains incorrect and it is far from being general. In a second part it is shown that important differences subsist between the Bayesian and frequentist approaches, when following the proposal of hep-ph/0701204 and inserting additional information on the hadronic amplitudes beyond isospin invariance. In particular the frequentist result preserves the exact degeneracy that is expected from the remaining symmetries of the problem while the Bayesian procedure does not. Moreover, in the Bayesian approach reducing inference to the 68% or 95% credible interval is a misconception of the meaning of the posterior PDF, which in turn implies that the significant dependence of the latter to the chosen parametrization cannot be viewed as a minor effect, contrary to the claim in hep-ph/0701204
Inclusive B-decay spectra and IR renormalons.
Full text linkI illustrate the role of infrared renormalons in computing inclusive B-decay spectra.
I explain the relation between the leading ambiguity in the definition of Sudakov
form factor exp(N /M) and that of the pole mass, and show how these ambiguities
cancel out between the perturbative and non-perturbative components of
the b-quark distribution in the meson
Search for pair-produced massive coloured scalars in four-jet final states with the ATLAS detector in proton–proton collisions at √s = 7 TeV
Full text linkContains fulltext :
111242.pdf (Publisher’s version ) (Open Access
Superluminal velocity through near-maximal neutrino oscillations or by being off shell
No full textRecently it was suggested that the observation of superluminal neutrinos by the OPERA collaboration may be due to group velocity effects resulting from close-to-maximal oscillation between neutrino mass eigenstates, in analogy to known effects in optics. We show that superluminal propagation does occur through this effect for a series of very narrow energy ranges, but this phenomenon cannot explain the OPERA measurement. Superluminal propagation can also occur if one of the neutrino masses is extremely small. However the effect only has appreciable amplitude at energies of order this mass and thus has negligible overlap with the multi-GeV scale of the experiment
Reply to: ''Improved Determination of the CKM Angle from decays''
No full text5 pages, 1 figure. Fig. 1 corrected (wrong file)In reply to hep-ph/0701204 we demonstrate why the arguments made therein do not address the criticism exposed in hep-ph/0607246 on the fundamental shortcomings of the Bayesian approach when it comes to the extraction of parameters of Nature from experimental data. As for the isospin analysis and the CKM angle alpha it is shown that the use of uniform priors for the observed quantities in the Explicit Solution parametrization is equivalent to a frequentist construction resulting from a change of variables, and thus relies neither on prior PDFs nor on Bayes' theorem. This procedure provides in this particular case results that are similar to the Confidence Level approach, but the treatment of mirror solutions remains incorrect and it is far from being general. In a second part it is shown that important differences subsist between the Bayesian and frequentist approaches, when following the proposal of hep-ph/0701204 and inserting additional information on the hadronic amplitudes beyond isospin invariance. In particular the frequentist result preserves the exact degeneracy that is expected from the remaining symmetries of the problem while the Bayesian procedure does not. Moreover, in the Bayesian approach reducing inference to the 68% or 95% credible interval is a misconception of the meaning of the posterior PDF, which in turn implies that the significant dependence of the latter to the chosen parametrization cannot be viewed as a minor effect, contrary to the claim in hep-ph/0701204
Matter Effect on Neutrino Oscillations from the violation of Universality in Neutrino Neutral Current Interactions
No full textThe violation of lepton-flavor-universality in the neutrinoZ interactions can lead to extra matter effects on neutrino oscillations at high energies, beyond that due to the usual charged-current interaction of the electron-neutrino. We show that the dominant effect of the violation is a shift in the effective value of θ23. This is in contrast to the dominant effect of the charged-current interaction which shifts θ12 and θ13. The shift in θ23 will be difficult to observe if the value of sin2(2θ23) is too close to one. However, if the value of sin2(2θ23) is as small as 0.92, then a Fermilab →Hyper-Kamiokande experiment can potentially place a constraint on universality violation at the 1% level after 5 years of data taking.archiveprefix: arXiv primaryclass: hep-ph reportnumber: OCHA-PP-257, YITP-06-01, VPI-IPPAP-06-02 slaccitation: %%CITATION = HEP-PH/0603268;%%false (Extension publication?
A New approach to inclusive decay spectra.
Full text linkThe main obstacle in describing inclusive decay spectra in QCD — which, in particular, limits
the precision in extrapolating the measured ¯B −→ Xs
rate to the full phase space as well as
in extracting |Vub| from inclusive measurements of charmless semileptonic decays — is their
sensitivity to the non-perturbative momentum distribution of the heavy quark in the meson.
We show that, despite this sensitivity, resummed perturbation theory has high predictive
power. Conventional Sudakov–resummed perturbation theory describing the decay of an onshell
heavy quark yields a divergent expansion. Detailed understanding of this divergence
in terms of infrared renormalons has paved the way for making quantitative predictions. In
particular, the leading renormalon ambiguity cancels out between the Sudakov factor and
the quark pole mass. This cancellation requires renormalon resummation but involves no
non-perturbative information. Additional effects due to the Fermi motion of the quark in
the meson can be systematically taken into account through power corrections, which are only
important near the physical endpoint. This way the moments of the ¯B −→ Xs
spectrum with
experimentally–accessible cuts — which had been so far just parametrized — were recently
computed by perturbative means. At Moriond these predictions were confronted with new
data from BaBar
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