arXiv subjects

Mark B. Wise

Publications and source records attributed to Mark B. Wise.

At least 109 records · Page 6Linked to original sources

arXiv2001

Comment on studying the corrections to factorization in B -> D(*) X

We propose studying the mechanism of factorization in exclusive decays of the form B->D(*)X by examining the differential decay rate as a function of the invariant mass of the light hadronic state X. If factorization works primarily due to the large N_c limit then its accuracy is not expected to decrease as the X invariant mass increases. However, if factorization is mostly a consequence of perturbative QCD then the corrections should grow with the X invariant mass. Combining data for hadronic tau decays and semileptonic B decays allows tests of factorization to be made for a variety of final states. We discuss the examples of B->D^*π^+π^-π^-π^0 and B->D^*ωπ^-. The mode B->D^*ωπ^- will allow a precision study of the dependence of the corrections to factorization on the invariant mass of the light hadronic state.

hep-ph↗

arXiv2000

Universal Asymptotic Behavior of Mortgage Prepayments

Mortgage prepayments play a crucial role in the pricing and hedging of mortgage backed securities. An important feature of mortgage prepayment modeling is burnout; as time goes on those borrowers who have the greatest tendency to refinance are removed from the pool leaving only those that are less likely to refinance. In this paper we examine the implications of burnout on the late time prepayment rate using rather general assumptions. Analytic formulas are derived for the average prepayment rate in the N'th month, P_N, and the fraction of borrowers left in the pool in the N'th month, y_N. In the case where the incentive to refinance, and other relevent economic factors, are constant these results are particularly simple. For example, P_N=p+(1-p)/N+... , where p is a constant and the ellipses denote terms suppressed by more powers of 1/N or exponentially suppressed. The term of order 1/N indicates that burnout causes the probability of prepayment to decrease as a very simple function of N.

nlin.AO↗

arXiv2000

Generalized *-Products, Wilson Lines and the Solution of the Seiberg-Witten Equations

Higher order terms in the effective action of noncommutative gauge theories exhibit generalizations of the *-product (e.g. *' and *-3). These terms do not manifestly respect the noncommutative gauge invariance of the tree level action. In U(1) gauge theories, we note that these generalized *-products occur in the expansion of some quantities that are invariant under noncommutative gauge transformations, but contain an infinite number of powers of the noncommutative gauge field. One example is an open Wilson line. Another is the expression for a commutative field strength tensor in terms of the noncommutative gauge field. Seiberg and Witten derived differential equations that relate commutative and noncommutative gauge transformations, gauge fields and field strengths. In the U(1) case we solve these equations neglecting terms of fourth order in the gauge field but keeping all orders in the noncommutative parameter.

hep-th↗

arXiv2000

Couplings of a Light Dilaton and Violations of the Equivalence Principle

Experimental discovery of the dilaton would provide strong evidence for string theory. A light dilaton could show up in current tests of the inverse square law for gravity at sub-millimeter distances. In the large extra dimension scenario, Kaluza-Klein excitations of the dilaton can also contribute to the cooling of supernovae. In order to quantify these effects we compute the couplings of a low energy dilaton to matter. These predominantly arise from the fundamental dilaton coupling to the gluon field strength, which receives a sizable enhancement from QCD scaling. We show that detection of the dilaton will give a direct measurement of the QCD coupling constant at the string scale. Particular attention is paid to the size of equivalence principle violating dilaton couplings.

hep-ph↗

arXiv2000

Quantum Field Theories With Compact Noncommutative Extra Dimensions

We study field theories on spaces with additional compact noncommutative dimensions. As an example, we study ϕ^3 on R^{1,3}\times T^{2}_θusing perturbation theory. The infrared divergences in the noncompact theory give rise to unusual dynamics for the mode of ϕwhich is constant along the torus. Correlation functions involving this mode vanish. Moreover, we show that the spectrum of Kaluza-Klein excitations can be very different from the analogous commuting theory. There is an additional contribution to the Kaluza-Klein mass formula that resembles the contribution of winding states in string theory. We also consider the effect of noncommutativity on the four dimensional Kaluza-Klein excitations of a six dimensional gauge field.

hep-th↗

arXiv2000

Conformal Invariance for Non-Relativistic Field Theory

Momentum space Ward identities are derived for the amputated n-point Green's functions in 3+1 dimensional non-relativistic conformal field theory. For n=4 and 6 the implications for scattering amplitudes (i.e. on-shell amputated Green's functions) are considered. Any scale invariant 2-to-2 scattering amplitude is also conformally invariant. However, conformal invariance imposes constraints on off-shell Green's functions and the three particle scattering amplitude which are not automatically satisfied if they are scale invariant. As an explicit example of a conformally invariant theory we consider non-relativistic particles in the infinite scattering length limit.

hep-th↗

arXiv1999

Phenomenology of a Stabilized Modulus

We explore the phenomenology of a stabilized modulus field in the Randall-Sundrum scenario. It is found that if the large separation between branes arises from a small bulk scalar mass then the modulus (i.e. radion) is likely to be lighter than the lowest Kaluza-Klein excitations of bulk fields, and consequently may be the first direct signature of the model. Four-dimensional general covariance completely determines the couplings of the modulus to Standard Model fields. The strength of these couplings is determined by a single parameter which is set by the TeV rather than the Planck scale.

hep-ph↗

arXiv1999

Modulus Stabilization with Bulk Fields

We propose a mechanism for stabilizing the size of the extra dimension in the Randall-Sundrum scenario. The potential for the modulus field that sets the size of the fifth dimension is generated by a bulk scalar with quartic interactions localized on the two 3-branes. The minimum of this potential yields a compactification scale that solves the hierarchy problem without fine tuning of parameters.

hep-ph↗

arXiv1999

Bulk Fields in the Randall-Sundrum Compactification Scenario

Recently, Randall and Sundrum proposed a solution to the hierarchy problem where the background spacetime is five dimensional. There are two 3-branes, and the mass scale for fields that propagate on one of the 3-branes is exponentially suppressed relative to the fundamental scale of theory, which is taken to be the Planck mass, M_Pl. In this letter we show that bulk fields with a five dimensional mass term of order M_Pl have, after integrating over the extra dimension, modes with four-dimensional masses that are exponentially suppressed as well. This opens the possibility that in this scenario the Standard Model matter fields may correspond to degrees of freedom that are not confined to a 3-brane.

hep-ph↗

arXiv1999

B -> K^* gamma from D -> K^* l nu

The B -> K^* gamma branching fraction is predicted using heavy quark spin symmetry at large recoil to relate the tensor and (axial-)vector form factors, using heavy quark flavor symmetry to relate the B decay form factors to the measured D -> K^* l nu form form factors, and extrapolating the semileptonic B decay form factors to large recoil assuming nearest pole dominance. This prediction agrees with data surprisingly well, and we comment on its implications for the extraction of |Vub| from B -> rho l nu.

hep-ph↗

arXiv1999

Power Counting For and Symmetries of the Effective Field Theory For NN Interactions

The appropriate power counting for the effective field theory of NN interactions is reviewed. It is more subtle than in most effective field theories since in the limit that the S-wave NN scattering lengths go to infinity it is governed by a nontrivial fixed point. The leading two body terms in the effective field theory for nucleon self interactions are scale invariant and invariant under Wigner SU(4) spin-isospin symmetry in this limit. Higher body terms with no derivatives (i.e., three and four body terms) are automatically invariant under Wigner symmetry.

hep-ph↗

arXiv1999

The B -> X_s gamma Photon Spectrum

The photon energy spectrum in inclusive weak radiative B -> X_s gamma decay is computed to order alpha_s^2 beta_0. This result is used to extract a value for the HQET parameter $\barΛ$ from the average <1-2E_γ/m_B>, and a value of the parameter $λ_1$ from <(1-2E_γ/m_B)^2>. An accurate measurement of <1-2E_γ/m_B> can determine the size of the nonperturbative contributions to the Upsilon(1S) mass which cannot be absorbed into the b quark pole mass.

hep-ph↗

arXiv1999

Wigner symmetry in the limit of large scattering lengths

We note that in the limit where the NN 1S0 and 3S1 scattering lengths, a^(1S0) and a^(3S1), go to infinity, the leading terms in the effective field theory for strong NN interactions are invariant under Wigner's SU(4) spin-isospin symmetry. This explains why the leading effects of radiation pions on the S-wave NN scattering amplitudes vanish as a^(1S0) and a^(3S1) go to infinity. The implications of Wigner symmetry for NN to NN axion and gamma d to n p are also considered.

hep-ph↗

arXiv1998

A Perturbative Calculation of the Electromagnetic Form Factors of the Deuteron

Making use of the effective field theory expansion recently developed by the authors, we compute the electromagnetic form factors of the deuteron analytically to next-to-leading order (NLO). The computation is rather simple, and involves calculating several Feynman diagrams, using dimensional regularization. The results agree well with data and indicate that the expansion is converging. They do not suffer from any ambiguities arising from off-shell versus on-shell amplitudes.

nucl-th↗

arXiv1998

n + p -> d + gamma in Effective Field Theory

The radiative capture process n+p-> d+gamma provides clear evidence for meson exchange currents in nuclear physics. We compute this process at low energies using a recently developed power counting for the effective field theory that describes nucleon-nucleon interactions. The leading order contribution to this process comes from the photon coupling to the nucleon magnetic moments. At subleading order there are other contributions. Among these are graphs where the photon couples directly to pions, i.e. meson exchange currents. These diagrams are divergent and require the presence of a local four-nucleon-one photon counterterm. The coefficient of this operator is determined by the measured cross section, 334.2 +- 0.5 mb, for incident neutrons with speed |v|=2200 m/s.

nucl-th↗

arXiv1998

An Effective Field Theory Calculation of the Parity Violating Asymmetry in n+p -> d+gamma

Weak interactions are expected to induce a parity violating pion-nucleon coupling, h_{πNN}^{(1)}. This coupling should be measurable in a proposed experiment to study the parity violating asymmetry A_γin the process \vec n + p \to d+γ. We compute the leading dependence of A_γon the coupling h_{πNN}^{(1)} using recently developed effective field theory techniques and find an asymmetry of A_γ= +0.17 h_{πNN}^{(1)} at leading order. This asymmetry has the opposite sign to that given by Desplanques, Donoghue and Holstein.

nucl-th↗

arXiv1998

Heavy Quark Physics

A review of Heavy Quark Effective Theory and Non Relativistic Quantum Chromondynamics is given. Some applications are discussed.

hep-ph↗

arXiv1998

Two-Nucleon Systems from Effective Field Theory

We elaborate on a new technique for computing properties of nucleon-nucleon interactions in terms of an effective field theory derived from low energy NN scattering data. Details of how the expansion is carried out to higher orders are presented. Analytic formulae are given for the amplitude to subleading order in both the 1S0 and 3S1-3D1 channels.

nucl-th↗