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P. H. Chankowski

Publications and source records attributed to P. H. Chankowski.

At least 19 recordsLinked to original sources

SUSY_FLAVOR v2.5: a computational tool for FCNC and CP-violating processes in the MSSM

We present SUSY_FLAVOR version 2.5 - a Fortran 77 program that calculates low-energy flavor observables in the general $R$-parity conserving MSSM. For a set of MSSM parameters as input, the code gives predictions for: 1. Electric dipole moments of the leptons and the neutron. 2. Anomalous magnetic moments (i.e. $g-2$) of the leptons. 3. Radiative lepton decays ($μ\to eγ$ and $τ\to μγ, eγ$). 4. Rare Kaon decays ($K^0_L\to π^0\barνν$ and $K^+\to π^+ \barνν$). 5. Leptonic $B$ decays ($B_{s,d}\to l^+ l^-$, $B\to τν$, $B\to D τν$ and $B\to D^\star τν$). 6. Radiative $B$ decays ($B\to\bar X_s γ$). 7. Rare decays of top quark to Higgs boson ($t\to ch,uh$). 8. $ΔF=2$ processes ($\bar K^0-K^0$, $\bar D-D$, $\bar B_d-B_d$ and $\bar B_s-B_s$ mixing). SUSY_FLAVOR performs the resummation of all chirally enhanced corrections, i.e. takes into account the effects enhanced by $\tanβ$ and/or large trilinear soft mixing terms to all orders in perturbation theory. All calculations are done using exact diagonalization of the sfermion mass matrices. Comparing to previous versions, in SUSY_FLAVOR v2.5 parameter initialization in SLHA2 format has been significantly generalized and simplified, so that program accepts without modifications most of the output files produced by other codes calculating MSSM spectra and processes. In addition, the routine calculating branching ratios for rare decays of top quark to Higgs boson has been included. The program can be obtained from www.fuw.edu.pl/susy_flavor.

hep-ph

Flavour physics of leptons and dipole moments

This chapter of the report of the ``Flavour in the era of the LHC'' Workshop discusses the theoretical, phenomenological and experimental issues related to flavour phenomena in the charged lepton sector and in flavour-conserving CP-violating processes. We review the current experimental limits and the main theoretical models for the flavour structure of fundamental particles. We analyze the phenomenological consequences of the available data, setting constraints on explicit models beyond the Standard Model, presenting benchmarks for the discovery potential of forthcoming measurements both at the LHC and at low energy, and exploring options for possible future experiments.

hep-ph

(Non)decoupling of the Higgs triplet effects

We consider the electroweak theory with an additional Higgs triplet at one loop using the hybrid renormalization scheme based on $α_{\rm EM}$, $G_F$ and $M_Z$ as input observables. We show that in this scheme loop corrections can be naturally split into the Standard Model part and corrections due to ``new physics''. The latter, however do not decouple in the limit of infinite triplet mass parameter, if the triplet trilinear coupling to SM Higgs doublets grows along with the the triplet mass. In electroweak observables computed at one loop this effect can be attributed to radiative generation in this limit of a nonvanishing vacuum expectation value of the triplet. We also point out that whenever tree level expressions for the electroweak observables depend on vacuum expectation values of scalar fields other than the Standard Model Higgs doublet, tadpole contribution to the ``oblique'' parameter $T$ should in principle be included. In the Appendix the origin of nondecoupling is discussed on the basis of symmetry principles in a simple scalar field theory.

hep-ph

Z' and the Appelquist-Carrazzone decoupling

We consider the electroweak theory with an additional neutral vector boson $Z^\prime$ at one loop. We propose a renormalization scheme which makes the decoupling of heavy $Z^\prime$ effects manifest. The proposed scheme justifies the usual procedure of performing fits to the electroweak data by combining the full SM loop corrections to observables with the tree level corrections due to the extended gauge structure. Using this scheme we discuss in the model with extra an $U(1)^\prime$ group factor 1-loop results for the $ρ$ parameters defined in several different ways.

hep-ph

Looking for CP violation in B -> tau+tau- decays

In supersymmetry with large tan(beta) the decays B0(B0bar) -> l+l- are dominated by the scalar and pseudoscalar Higgs penguin diagrams leading to strong enhancement of leptonic decay rates with potentially large CP asymmetries in the tau+tau- decay modes measurable in BELLE or BaBar experiments. The TAUOLA tau-lepton decay library supplemented by its universal interface can efficiently be used to search for B0(B0bar) -> tau+tau- decays, and to investigate how the CP asymmetry is reflected in realistic experimental observables.

hep-ph

Flavour Changing Neutral Currents and Inverted Sfermion Mass Hierarchy

We study the contraints on non-flavour-blind soft supersymmetry breaking terms coming from flavour and CP violating processes in the presence of hierarchical Yukawa couplings, and quantify how much these constraints are weakened in the regions of the MSSM parameter space characterized by heavy gauginos and multi-TeV sfermion masses, respectively. We also study the inverted sfermion mass hierarchy scenario in the context of D-term supersymmetry breaking, and show that generic hierarchical Yukawa couplings with arbitrary phases require first generation squarks in the few 10 TeV range.

hep-ph

Update on Fermion Mass Models with an Anomalous Horizontal U(1) Symmetry

We reconsider models of fermion masses and mixings based on a gauge anomalous horizontal U(1) symmetry. In the simplest model with a single flavon field and horizontal charges of the same sign for all Standard Model fields, only very few charge assignements are allowed when all experimental data, including neutrino oscillation data, is taken into account. We show that a precise description of the observed fermion masses and mixing angles can easily be obtained by generating sets of the order one parameters left unconstrained by the U(1) symmetry. The corresponding Yukawa matrices show several interesting features which may be important for flavour changing neutral currents and CP violation effects in supersymmetric models.

hep-ph

Effects of the scalar FCNC in $b\to sl^+l^-$ transitions and supersymmetry

We investigate the potential effects of the scalar flavour changing neutral currents that are generated e.g. in supersymmetry with $\tanβ\gg1$ in the $b\to sl^+l^-$ transitions. Using the experimental upper limit on $BR(B^0_s\toμ^+μ^-)$ we place stringent model independent constraints on the impact these currents may have on the rates $BR(B\to X_sμ^+μ^-)$ and $BR(B\to Kμ^+μ^-)$. We find that in the first case, contrary to the claim made recently in the literature, the maximal potential effects are always smaller than the uncertainty of the Standard Model NNLO prediction, that is of order 5-15%. In the second case, the effects can be large but the experimental errors combined with the unsettled problems associated with the relevant formfactors do not allow for any firm conclusion about the detectability of a new physics signal in this process. In supersymmetry the effects of the scalar flavour changing neutral currents are further constrained by the experimental lower limit on the $B^0_s$-$\bar B^0_s$ mass difference, so that most likely no detectable signal of the supersymmetry generated scalar flavour changing neutral currents in processes $B\to X_sμ^+μ^-$ and $B\to Kμ^+μ^-$ is possible.

hep-ph

Limits on $T_{RH}$ for thermal leptogenesis with hierarchical neutrino masses

We make a simple observation that if one of the right-chiral neutrinos is very heavy or its Yukawa couplings to the standard lepton doublets are negligible, so that it effectively decouples from the see-saw mechanism, the prediction for the baryon asymmetry of the Universe resulting from leptogenesis depends, apart from the masses $M_1$ and $M_2$ of the remaining two right-chiral neutrinos, only on the element $\YY{22}$ of the neutrino Yukawa coupling. For $M_2\simgt10M_1$ the lower bound on $M_1$ and also on $T_{\rm reh}$, resulting from the requirement of 'successful leptogenesis' is then significantly increased compared to the one computed recently by Buchmüller {\it et al.} in the most general case. Within the framework of thermal leptogenesis, the only way to lower this limit is then to allow for sufficiently small mass difference $M_2-M_1$.

hep-ph

$ΔM_{d,s}$, $B^0_{d,s}\toμ^+μ^-$ and $B\to X_sγ$ in Supersymmetry at Large $\tanβ$

We present an effective Lagrangian formalism for the calculation of flavour changing neutral and charged scalar currents in weak decays including $SU(2)\times U(1)$ symmetry breaking effects and the effects of the electroweak couplings $g_1$ and $g_2$. We apply this formalism to the MSSM with large $\tanβ$ with the CKM matrix as the only source of flavour violation, heavy supersymmetric particles and light Higgs bosons. We give analytic formulae for the neutral and charged Higgs boson couplings to quarks including large $\tanβ$ resummed corrections in the $SU(2) \times U(1)$ limit and demonstrate that these formulae can only be used for a semi-quantitative analysis. In particular they overestimate the effects of large $\tanβ$ resummed corrections. We give also improved analytic formulae that reproduce the numerical results of the full approach within $5-10%$. We present for the first time the predictions for the branching ratios $B^0_{s,d}\to μ^+μ^-$ and the $B^0_{d,s}-\bar B^0_{d,s}$ mass differences $ΔM_{d,s}$ that include simultaneously the resummed large $\tanβ$ corrections, $SU(2)\times U(1)$ breaking effects and the effects of the electroweak couplings. We perform an anatomy of the correlation between the increase of the rates of the decays $B^0_{s,d}\toμ^+μ^-$ and the suppression of $ΔM_s$, that for large $\tanβ$ are caused by the enhanced flavour changing neutral Higgs couplings to down quarks. We take into account the constraint from $B\to X_s γ$ clarifying some points in the calculation of the large $\tanβ$ enhanced corrections to this decay.

hep-ph

Correlation between Delta M_s and B^0_{s,d} --> mu^+ mu^- in Supersymmetry at Large tan beta

Considering the MSSM with the CKM matrix as the only source of flavour violation and heavy supersymmetric particles at large $\tanβ$, we analyze the correlation between {\it the increase} of the rates of the decays $B^0_{s,d}\to μ^+μ^-$ and {\it the suppression} of $ΔM_s$, that are caused by the enhanced flavour changing neutral Higgs couplings to down-type quarks. We give analytic formulae for the neutral and charged Higgs couplings to quarks including large $\tanβ$ resummed corrections in the $SU(2)\times U(1)$ limit and comment briefly on the accuracy of this approximation. For $0.8\le (ΔM_s)^{\rm exp}/(ΔM_s)^{\rm SM}\le 0.95$ we find $6\cdot 10^{-7}\ge BR(B^0_s\ra μ^+μ^-)^{\rm max} \ge 4\cdot 10^{-8}$ and $1.4\cdot 10^{-8}\ge BR(B^0_d\ra μ^+μ^-)^{\rm max}\ge 1\cdot 10^{-9}$. For $(ΔM_s)^{\rm exp} \ge (ΔM_s)^{\rm SM}$ substantial enhancements of $B^0_{s,d}\raμ^+μ^-$ relative to the expectations based on the Standard Model are excluded. With $(ΔM_s)^{\rm exp}>15.0/$ps a conservative analysis of $(ΔM_s)^{\rm SM}$ gives $BR(B^0_s\ra μ^+μ^-)\simlt1.2\cdot10^{-6}$ and $BR(B^0_d\ra μ^+μ^-)\simlt3\cdot10^{-8}$. However, we point out that in the less likely scenario in which the squark mixing is so large that the neutral Higgs contributions dominate $ΔM_s$, the rates for $B^0_{s,d}\to μ^+μ^-$ increase with increasing $ΔM_s$ and the bounds in question are weaker. Violation of all these correlations and bounds would indicate new sources of flavour violation.

hep-ph

Supersymmetry (at large tan beta) and flavour physics

Recent development in exploring flavour dynamics in the supersymmetric extension of the Standard Model is reviewed. Emphasis is put on possible interesting effects in b-physics arising for large values of tan beta both in the case of minimal flavour violation and in the case of flavour violation originating in the sfermion sector. The importance of the flavour changing neutral Higgs boson couplings generated by the scalar penguin diagrams and their role in the interplay of neutral B-meson mixing and B^0_{d,s} --> mu^+ mu^- decays is discussed. It is pointed out that observation of the B^0_d --> mu^+ mu^- decay with BR at the level $\simgt 3 X 10^{-8}$ would be a strong indication of nonminimal flavour violation in the quark sector. Possible impact of flavour violation in the slepton sector on neutrino physics is also discussed.

hep-ph

Quantum corrections to neutrino masses and mixing angles

Contents: 1. Introduction 2. Fermion masses and mixing 3. Neutrino masses in the effective theory 4. Quantum corrections from the renormalization group evolution 4.1. RG equations for the CKM matrix 4.2. RG equations for neutrino masses and mixing angles 4.3. Evolution of the neutrino masses 4.4. Mixing of two neutrinos 4.5 Mixing of three neutrinos and fixed points 5. Low energy threshold corrections 5.1. Threshold corrections in the SM 5.2. Threshold corrections in the MSSM 5.2.1. Three-fold degeneracy and flavour diagonal corrections 5.2.2. Three-fold degeneracy and flavour non-diagonal corrections 5.2.3. Two-fold degeneracy and threshold corrections 6. Conclusions, Appendix A, Appendix B, References.

hep-ph

Low energy threshold corrections to neutrino masses and mixing angles

We compute the low energy threshold corrections to neutrino masses and mixing in the Standard Model (SM) and its minimal supersymmetric version, using the effective theory technique. We demonstrate that they stabilize the renormalization group (RG) running with respect to the choice of the scale to which the RG equation is integrated. This confirms the correctness of the recent re-derivation of the RGE for the SM in hep-ph/0108005. The explicit formulae for the low energy threshold corrections corrections can be applied to specific models of neutrino masses and mixing.

hep-ph

Neutrino Unification

Present neutrino data are consistent with neutrino masses arising from a common seed at some ``neutrino unification'' scale $M_X$. Such a simple theoretical ansatz naturally leads to quasi-degenerate neutrinos that could lie in the electron-volt range with neutrino mass splittings induced by renormalization effects associated with supersymmetric thresholds. In such a scheme the leptonic analogue of the Cabibbo angle $θ_{\odot}$ describing solar neutrino oscillations is nearly maximal. Its exact value is correlated with the smallness of $θ_{reactor}$. These features agree both with latest data on the solar neutrino spectra and with the reactor neutrino data. The two leading mass-eigenstate neutrinos present in \ne form a pseudo-Dirac neutrino, avoiding conflict with neutrinoless double beta decay.

hep-ph

$B^0_{d,s}\to μ^-μ^+$ in the MSSM

We present the results of the complete one-loop computation of the $B^0_{d,s}\to l^+l^-$ decay rate in the MSSM. Both sources of the FCNC, the CKM matrix and off-diagonal entries of the sfermion mass matrices are considered. Strong enhancement of the branching ratio (compared to the SM prediction) can be obtained in the large $\tanβ\sim m_t/m_b$ regime in which the neutral Higgs boson ``penguin'' diagrams dominate. We make explicit the strong dependence of this enhancement on the top squarks mixing angle in the case of the chargino contribution and on the $μ$ parameter in the case of the gluino contribution. We show that, in some regions of the MSSM parametre space, the branching ratio for this process can be as large as $10^{-(5-4)}$ respecting all existing constraints, including the CLEO measurement of $BR(B\to X_sγ)$. We also estimate, that for chargino and stop masses $\sim{\cal O}(100$ GeV) $BR(B^0_s\to l^+l^{\prime -})$ with $ll^\prime=eτ$ or $μτ$ can be of the order of $10^{-11}$ for the still allowed values of the off-diagonal entries in the slepton mass matrix.

hep-ph

Fixed points in the evolution of neutrino mixings

We derive the renormalization group equations for the neutrino masses and mixing angles in explicit form and discuss the possible classes of their solutions. We identify fixed points in the equations for mixing angles, which can be reached during the evolution for several mass patterns and give $\sin^22θ_{sol}=\sin^22θ_{atm}\sin^2θ_3/ (\sin^2θ_{atm}\cos^2θ_3 + \sin^2θ_3)^2$, consistently with the present experimental information. Further experimental test of this relation is of crucial interest. Moreover, we discuss the stability of quantum corrections to neutrino mass squared differences. Several interesting mass patterns show stability in the presence of fixed point solutions for the angles.

hep-ph

Implications of the precision data for very light Higgs boson scenario in 2HDM(II)

We present an up-to-date analysis of the constraints imposed bythe precision data on the ($CP-$ conserving) Two-Higgs-Doublet Model of type II, with emphasis on the possible existence of very light neutral (pseudo)scalar Higgs boson with mass below 20--30 GeV. We show that even in the presence of such light particles, the 2HDM(II) can describe the electroweak data with precision comparable to that given by the SM. Particularly interesting lower limits on the mass of the lighter neutral $CP-$even scalar $h^0$ are obtained in the scenario with a light $CP-$odd Higgs boson $A^0$ and large $\tanβ$.

hep-ph