arXiv subjects

K. Maltman

Publications and source records attributed to K. Maltman.

At least 55 records · Page 3Linked to original sources

arXiv2007

Joint Extraction of m_s and V_us from Hadronic Tau Decays

We study the simultaneous determination of m_s and V_us from flavor-breaking hadronic tau decay sum rules using weights designed to bring under better control problems associated with the slow convergence of the relevant D=2 OPE series. Much improved stability and consistency is found as compared to the results of conventional analyses based on the ``(k,0) spectral weights''. Results for m_s are in excellent agreement with those of recent strange scalar and strange pseudoscalar sum rule analyses, as well as recent lattice analyses, while those for V_us agree within errors with the output from recent lattice-based Gamma[K_{mu 2}]/Gamma[pi_{mu 2}] and K_{\ell 3}-based analyses. Very significant error reductions are shown to be expected, especially for V_us, once the improved strange spectral data from the B factory experiments becomes available.

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arXiv2006

The Joint Extraction of m_s and V_us From Hadronic Tau Decay Data

We discuss the simultaneous determination of m_s and V_us from flavor-breaking hadronic tau decay sum rules, focussing on weight choices designed to better control problems associated with the slow convergence of the relevant integrated D=2 OPE series. The results are found to display improved stability and consistency relative to those of conventional analyses based on the ``(k,0) spectral weights''. The results for m_s agree well with those of recent strange scalar sum rule and strange pseudoscalar sum rule and lattice analyses. Results for V_us agree within errors with those of lattice-input-based K_{ell 3} and Gamma [K_{mu 2}]/Γ[pi_{mu 2}] analyses. Very significant error reductions are shown to be expected, especially for V_us, once improved strange spectral data from the B factory experiments becomes available.

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arXiv2006

V_us From Hadronic Tau Decays

We study extractions of |V_us| based on finite energy sum rule (FESR) analyses of hadronic tau decay data. We show (i) that the ``(0,0) spectral weight'' implementation (proposed previously in the literature as a favorable version of this analysis) suffers from significant convergence problems, but (ii) that alternate implementations exist which bring these problems under control. Results based on present spectral data are shown to be in agreement with those of other approaches, though with, at present, somewhat larger experimental errors. Sub-1% determinations of |V_us| are also shown to be expected from these alternate analyses once tau data from the B factories becomes available.

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arXiv2004

Issues in the Extraction of m_s and V_us from Hadronic Tau Decay Data

Various complications encountered in the process of attempting to extract the basic Standard Model parameters, m_s and V_us, from hadronic tau decay data are discussed. Preliminary results for V_us, based on sum rules displaying good convergence and stability, are also presented.

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arXiv2004

Constituent quark models and pentaquark baryons

We discuss certain general features of the pentaquark picture for the theta, its 10bar_F partner, Xi_{3/2}, and possible heavy quark analogues. Models employing spin-dependent interactions based on either effective Goldstone boson exchange or effective color magnetic exchange are also used to shed light on possible corrections to the Jaffe-Wilczek and Karliner-Lipkin scenarios. Some model-dependent features of the pentaquark picture (splitting patterns and relative decay couplings) are also discussed in the context of these models.

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arXiv2004

Heavy Antiquark Pentaquarks in the CM and GB Models

The splittings between positive parity pentaquarks containing a single heavy (c,b) antiquark and four light (u,d) quarks are investigated in models having spin-dependent interactions generated by either effective Goldstone boson exchange or effective color magnetic exchange. Model-independent features of these splittings are emphasized. Overlaps to the ``fall-apart'' decay configurations ND, ND* or NB, NB*, relevant to decay couplings for the various 2-body pentaquark decays, are also computed.

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arXiv2003

QCD Condensates for the Light Quark V-A Correlator

We use the procedure of pinched-weight Finite Energy Sum Rules (pFESR) to determine the OPE coefficients a_6, ...,a_16 of the flavor ud V-A correlator in terms of existing hadronic tau decay data. We show by appropriate weight choices that the error on the dominant d=6 contribution, which is known to be related to the K -> Pi Pi matrix elements of the electroweak penguin operator in the chiral limit, may be reduced to below the ~15% level. The values we obtain for the OPE coefficients with d>8 are shown to naturally account for the discrepancies between our results for the d=6 and d=8 terms and those of previous analyses, which were obtained neglecting d>8 contributions.

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arXiv2002

K -> pi pi Electroweak Penguins in the Chiral Limit

We report on dispersive and finite energy sum rule analyses of the electroweak penguin matrix elements < (pi pi) | Q_{7,8} | K > in the chiral limit. We accomplish the correct perturbative matching (scale and scheme dependence) at NLO in alpha_s, and we describe two different strategies for numerical evaluation.

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arXiv2000

The Strange Quark Mass From Flavor Breaking in Hadronic Tau Decays

The strange quark mass is extracted from a finite energy sum rule (FESR) analysis of the flavor-breaking difference of light-light and light-strange quark vector-plus-axial-vector correlators, using spectral functions determined from hadronic tau decay data. We point out problems for existing FESR treatments associated with potentially slow convergence of the perturbative series for the mass-dependent terms in the OPE over certain parts of the FESR contour, and show how to construct alternate weight choices which not only cure this problem, but also (1) considerably improve the convergence of the integrated perturbative series, (2) strongly suppress contributions from the region of s values where the errors on the strange current spectral function are still large and (3) essentially completely remove uncertainties associated with the subtraction of longitudinal contributions to the experimental decay distributions. The result is an extraction of m_s with statistical errors comparable to those associated with the current experimental uncertainties in the determination of the CKM angle, V_{us}. We find m_s(1 GeV)=158.6\pm 18.7\pm 16.3\pm 13.3 MeV (where the first error is statistical, the second due to that on V_{us}, and the third theoretical).

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arXiv2000

The Strong Isospin-Breaking Correction for the Gluonic Penguin Contribution to epsilon'/epsilon at Next-to-Leading Order in the Chiral Expansion

The strong isospin-breaking correction, Omega_{st}, which appears in estimates of the Standard Model value for the direct CP-violating ratio epsilon'/epsilon, is evaluated to next-to-leading order (NLO) in the chiral expansion using Chiral Perturbation Theory. The relevant linear combinations of the unknown NLO CP-odd weak low-energy constants (LEC's) which, in combination with 1-loop and strong LEC contributions, are required for a complete determination at this order, are estimated using two different models. It is found that, to NLO, Omega_{st}=0.08 +/- 0.05, significantly reduced from the ``standard'' value, 0.25 +/- 0.08, employed in recent analyses. The potentially significant numerical impact of this decrease on Standard Model predictions for epsilon'/epsilon, associated with the decreased cancellation between gluonic penguin and electroweak penguin contributions, is also discussed.

hep-ph↗

arXiv2000

Strong Isospin Breaking in CP-even and CP-odd K -> pi pi Decays

Complete next-to-leading (chiral) order (NLO) expressions for the strong isospin-breaking (IB) contributions in K -> pi pi are used to discuss (1) for CP-even, the impact on the magnitude of the Delta I=1/2 Rule, and (2) for CP-odd, the strong IB correction, Omega_st, for the gluonic penguin contribution to epsilon'/epsilon, with particular emphasis on the strong low-energy constant (LEC) and loop contributions, numerical values for which are model-independent at NLO.

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arXiv2000

Extracting m_s From Flavor Breaking in Hadronic Tau Decays

New finite energy sum rules (FESR's) for extracting m_s from hadronic tau decay data are constructed which (1) significantly reduce potential theoretical uncertainties present in existing sum rule analyses and (2) remove problems associated with both the poor convergence of the OPE representation of the longitudinal part of the $us$ vector and axial vector correlators and the large statistical errors in the $us$ spectral data above the K^* region.

hep-ph↗

arXiv2000

O(m_d-m_u) Effects in CP-even and CP-odd K-->pi pi Decays

Strong isospin-breaking (IB) effects in CP-even and CP-odd K-->pi pi decays are computed to next-to-leading order (NLO) in the chiral expansion. The impact of these corrections on the magnitude of the Delta I=1/2 Rule and on the size of the IB correction, Omega_IB, to the gluonic penguin contribution to epsilon'/epsilon are discussed.

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arXiv2000

Scalar Meson Decay Constants and the Nature of the a_0(980)

The a_0(980), a_0(1450) and K_0(1430) decay constants are determined using a form of QCD sum rules known to produce a very accurate determination of the rho decay constant. The ratio of a_0(980) to K_0(1430) decay constants is shown to be ~0.6, ruling out both the ``loosely-bound-K\bar{K}-molecule'' and Gribov minion scenarios for the a_0(980). Solutions for the isovector scalar spectral function obtained in the literature from sum rule analyses employing a more restrictive single-resonance-plus-continuum form of the input spectral ansatz, are also investigated. These solutions, which suggest, in contrast to the present results, negligible coupling of the a_0(980) to the isovector scalar density are shown to produce a poor quality match between the OPE and hadronic sides of the sum rules employed here, and hence to be strongly disfavored relative to the present solution.

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arXiv2000

Isospin Breaking in the Extraction of Isovector and Isoscalar Spectral Functions from e^+e^- --> hadrons

A finite energy sum rule (FESR) analysis of the isospin-breaking vector current correlator <0|T(V^3_μV^8_ν)|0> is used to determine the isospin-breaking electromagnetic (EM) decay constants of the low-lying vector mesons. These results are used to evaluate the corrections required to extract the flavor diagonal 33 and 88 resonance contributions from the full resonance EM contributions to the EM spectral function. A large (~15%) correction is found in the case of the omega contribution to the isoscalar spectral function. The implications of these results for sum rules based on the isovector-isoscalar spectral difference are considered.

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arXiv1999

The $a_0(980)$, $a_0(1450)$ and $K_0^*(1430)$ Scalar Decay Constants and the Isovector Scalar Spectrum

The isovector scalar correlator is studied using a class of finite energy sum rules shown recently to be very well satisfied in the vector isovector channel. The values of the $a_0$ scalar decay constants extracted in this analysis, which describe the couplings of the $a_0(980)$ and $a_0(1450)$ to the isovector scalar current, are shown to be comparable, strongly disfavoring any scenario in which the $a_0(980)$ is interpreted as a loosely bound $K\bar{K}$ molecule and the $a_0(1450)$ is assigned to the same flavor multiplet as the $K_0^*(1430)$. The $a_0$ decay constants are also compared to the analogous decay constant describing the coupling of the $K_0^*(1430)$ to the divergence of the strange vector current (which may be obtained from experimental $K_{e3}$ and $Kπ$ phase shift data), and implications of the relative magnitudes for the interpretation of the nature of the $a_0$ states discussed.

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arXiv1999

The Strange Quark Mass From Finite Energy Sum Rules

The strange quark mass is determined from a study of the correlator of the divergence of the strange vector current using a family of finite energy sum rules recently shown to be very accurately satisfied in the isovector vector channel. It is shown that the match between the OPE and hadronic representations for the sum rules employed is extremely good once one fixes the overall scale, (m_s-m_u), which normalizes the OPE side. A value $m_s=115\pm 8$ MeV at a scale 2 GeV, corresponding to $m_s=159\pm 11$ MeV at a scale 1 GeV, is obtained, with theoretical and experimental uncertainties contributing roughly equally to the combined error.

hep-ph↗

arXiv1999

Constraints on Hadronic Spectral Functions From Continuous Families of Finite Energy Sum Rules

Hadronic tau decay data is used to study the reliability of various finite energy sum rules (FESR's). For intermediate scales (of order 2-3 GeV^2), those FESR's with weights s^k are found to have significant errors, whereas those with weights having a zero at the juncture (s=s_0) of the cut and circular part of the contour work very well. It is also shown that a combination of two such sum rules allows rather strong constraints to be placed on the hadronic spectral function without sacrificing the excellent agreement between OPE and hadronic representations. The method then is applied to the strangeness -1 and pseudoscalar isovector channels, where it is shown to provide novel constraints on those ansatze for the unmeasured continuum parts of the spectral functions employed in existing extractions of m_u+m_d, m_s. The continuum ansätz in the latter channel, in particular, is shown to produce a rather poor match to the corresponding OPE representation, hence re-opening the question of the value of the light quark mass combination m_u+m_d.

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