scholarly journals A New Energy-dependent Δ Width in Coherent Pion Production

1999 ◽  
Vol 52 (6) ◽  
pp. 955 ◽  
Author(s):  
P. A. Deutchman
Keyword(s):  
Form Factor ◽  
Pion Production ◽  
Bound State ◽  
Momentum Dependence ◽  
Energy Distributions ◽  
Particle Decay ◽  
Pion Energy ◽  
New Energy ◽  
Vertex Form Factor ◽  
Energy Dependent

A new derivation for the energy-dependent Δ width inside nuclei is presented which includes the all important, energy-dependent nuclear form factor describing the decay of the Δ particle from its harmonic oscillator, bound state back to a captured nucleon and outgoing pion. Additional improvements include relativistic kinematics, generalisation beyond the static limit in the kinematics, and inclusion of the ΔN Π energy-dependent vertex form factor. The new decay width provides a reasonable cut-off at high pion momenta and gives the correct momentum dependence in the limit of single-particle decay at low momenta. The results of calculations for the energy-dependent widths and their effects on the energy distributions of exclusive coherent pion production for 12 C+ 12 C → 12 C+ 12 C* (T = 1)+ Π 0 at incident energies below and above the pion threshold are shown and discussed. The new energy dependence is compared to the free Δ width used previously and it is seen that the new results give a smoother and more realistic shape to the pion energy distributions.

Origins of the energy distribution structure in coherent pion production at intermediate energies

2001 ◽  
Vol 79 (8) ◽  
pp. 1055-1074 ◽  
Author(s):  
P A Deutchman
Keyword(s):  
Incident Energy ◽  
Giant Resonance ◽  
Intermediate Energy ◽  
Hole State ◽  
Energy Distributions ◽  
Intermediate Energies ◽  
Pion Energy ◽  
Three Body ◽  
Energy Dependent ◽  
First Time

New calculations have been done that now cover the intermediate energy range from 100 MeV/nucleon to 2.0 GeV/nucleon incident energy for the reaction 12C + 12C [Formula: see text] 12C + 12C (15.11 MeV) +π0, where constructive, coherent Δ-hole states are excited in either nucleus while the companion nucleus is excited to a coherent nucleon–hole state describing the spin–isospin, giant resonant state at 15.11 MeV. The Δ (1232 MeV) isobar then decays to a nucleon and pion. Theoretical pion energy distributions are calculated and, for the first time, results above 400 MeV/nucleon are shown. A theoretical basis for understanding how the shapes of the pion distributions change as a function of incident energy is described. The fundamental shape of the Δ-production amplitude as a function of momentum transfer is discussed and the effects of the energy-dependent nuclear width are examined. Furthermore, the connection between the origins of the pion distribution to the final pion shapes is made and the importance of the giant resonance in providing an important signature is pointed out. By pushing the calculations above 400 MeV/nucleon, it was discovered that sliding kinematics and kinematic turnarounds occur due to the two-to-three-body sequential nature of the reactions and these effects determine the final structure of the pion distributions at higher incident energies. PACS Nos.: 24.10Cn, 24.30Cz, 25.70-z, 25.80-e

scholarly journals CALCULATING TWO- AND THREE-BODY DECAYS WITH FeynArts AND FormCalc

2003 ◽  
Vol 14 (09) ◽  
pp. 1273-1278 ◽  
Author(s):  
MICHAEL KLASEN
Keyword(s):  
Standard Model ◽  
Particle Production ◽  
High Energy Physics ◽  
High Energy ◽  
Energy Distributions ◽  
Particle Decay ◽  
The Standard Model ◽  
Decay Widths ◽  
Three Body ◽  
Energy Physics

The Feynman diagram generator FeynArts and the computer algebra program FormCalc allow for an automatic computation of 2→2 and 2→3 scattering processes in High Energy Physics. We have extended this package by four new kinematical routines and adapted one existing routine in order to accomodate also two- and three-body decays of massive particles. This makes it possible to compute automatically two- and three-body particle decay widths and decay energy distributions as well as resonant particle production within the Standard Model and the Minimal Supersymmetric Standard Model at the tree- and loop-level. The use of the program is illustrated with three standard examples: [Formula: see text], [Formula: see text], and [Formula: see text].

CHIRAL QCD GENERATES CONSTITUENT QUARK MASSES

1988 ◽  
Vol 03 (16) ◽  
pp. 1595-1602 ◽  
Author(s):  
J. PRASCHIFKA ◽  
R.T. CAHILL ◽  
C.D. ROBERTS
Keyword(s):  
Form Factor ◽  
Quark Mass ◽  
Constituent Quark ◽  
Bound State ◽  
Variational Technique ◽  
Quark Masses ◽  
Constituent Quark Mass ◽  
Insight Into

Constituent quark masses are shown to arise naturally in an approximation to chiral QCD. The colour [Formula: see text] diquark component of the nucleon is studied using a new variational technique to solve a Bethe-Salpeter equation for this qq bound state in massless QCD. The resultant diquark form factor Γ(q) exhibits a dramatic peaking for (Euclidean) momentum q2≈(0.2 GeV )2 which, we show, signals the generation of a constituent quark mass of ≈270 MeV , and which provides a significant insight into deep inelastic leptonnucleon scattering results.

Pion structure in a modified quark loop model

1980 ◽  
Vol 58 (7) ◽  
pp. 964-968 ◽  
Author(s):  
J. H. Kim ◽  
L. Resnick
Keyword(s):  
Form Factor ◽  
Bound State ◽  
Weak Decay ◽  
Loop Model ◽  
Vector Structure ◽  
Pion Structure ◽  
The One ◽  
System Coupling ◽  
State Nature ◽  
Good Agreement

The pion is assumed as usual to couple to the electroweak currents through its constituent quarks. The bound state nature of the [Formula: see text] system coupling to the electroweak currents is simulated by a form factor at the [Formula: see text] vertex, parametrized by an effective mass M and coupling strength f. Calculations are performed at the one loop level, with a prescription used to ensure electromagnetic gauge invariance. Isospin invariance is assumed. f, M, and the effective quark mass m are determined by the normalization condition for the pion electromagnetic form factor and the charged and neutral pion lifetimes. The charge radius of the pion is calculated and found to be in good agreement with experiment. The ratio of the axial to vector structure functions in the radiative weak decay π → evγ is also determined.

The charge form factor of the model triton for two-particle interactions with continuum bound states

1981 ◽  
Vol 59 (2) ◽  
pp. 225-230 ◽  
Author(s):  
G. Pantis ◽  
H. Fiedeldey ◽  
D. W. L. Sprung
Keyword(s):  
Form Factor ◽  
Bound States ◽  
Bound State ◽  
Interesting Case ◽  
Charge Form Factor ◽  
Particle Interactions ◽  
Charge Form ◽  
Nonlocal Interactions ◽  
Asymptotic Shape ◽  
Three Body

The charge form factor of the model triton clearly exhibits the collapse which occurs in the triton for purely nonlocal two-body interactions with continuum bound states and approaches an asymptotic shape with increasing binding energy. However, partly nonlocal interactions with continuum bound states, which previously have been shown not to produce such a collapse, also show no evidence whatsoever of the presence of the two-particle continuum bound state in the triton charge form factor. In the physically interesting case of partly nonlocal interactions the occurrence of a continuum bound state in the two-body interactions therefore can be completely harmless in the three-body system.

scholarly journals Virtuality Distributions and Pion Transition Form Factor

2015 ◽  
Vol 37 ◽  
pp. 1560050
Author(s):  
A. V. Radyushkin
Keyword(s):  
Form Factor ◽  
Transverse Momentum ◽  
Momentum Distribution ◽  
Transition Form Factor ◽  
Transition Process ◽  
Transverse Momentum Distribution ◽  
Momentum Dependence ◽  
Matrix Elements ◽  
Transition Form ◽  
New Approach

Using the example of hard exclusive transition process γ*γ → π0 at the handbag level, we outline basics of a new approach to transverse momentum dependence in hard processes. In coordinate representation, matrix elements of operators (in the simplest case, bilocal 𝒪(0, z)) describing a hadron with momentum p, are functions of (pz) and z2 parametrized through virtuality distribution amplitudes (VDA) Φ(x, σ), with x being Fourier-conjugate to (pz) and σ Laplace-conjugate to z2. For intervals with z+ = 0, we introduce the transverse momentum distribution amplitude (TMDA) Ψ(x, k⊥), and write it in terms of VDA Φ(x, σ). We propose models for soft VDAs/TMDAs, and use them for comparison of handbag results with experimental (BaBar and BELLE) data. We also discuss the generation of hard tails of TMDAs from initially soft forms.

scholarly journals CONSTRAINTS ON THE ELECTROWEAK UNIVERSAL PARAMETERS AND THE TOP AND HIGGS MASSES FROM UPDATED LEP/SLC DATA

1995 ◽  
Vol 10 (33) ◽  
pp. 2553-2569 ◽  
Author(s):  
SEIJI MATSUMOTO
Keyword(s):  
Form Factor ◽  
Higgs Boson ◽  
Top Quark ◽  
Higgs Mass ◽  
Global Analysis ◽  
Mean Value ◽  
The Standard Model ◽  
The Mean ◽  
The Masses ◽  
Vertex Form Factor

A global analysis is performed using the recent data from LEP and SLC. Constraints on the electroweak universal parameters (S, T, U) and on the masses of the top quark and Higgs boson within the standard model (SM) are investigated. The uncertainties due to the QCD and QED effective couplings, αs(mz) and , [Formula: see text] are examined in detail. Even though the mean value of S is increased to be consistent with zero, the naive Technicolor models are still disfavored due to its reduced error. Within the SM, we find the 90% CL constraints; 133 GeV<mt<190 GeV and 10 GeV<mH< 440 GeV for αs(mz)=0.116 and [Formula: see text]. The experimental constraints on the ZbLbL vertex form factor, [Formula: see text] play an important role in disfavoring the region of large mt(mt~200GeV) and large mH(mH~1000 GeV). If mt is precisely known, the present electroweak data give a rather strict upper bound on the Higgs mass, mH<140(300) GeV at 95% CL, for mt=160(175) GeV and for the above αs(mz) and [Formula: see text].

scholarly journals TWO-PION PRODUCTION IN ELECTRON-POLARIZED PROTON SCATTERING

2013 ◽  
Vol 28 (12) ◽  
pp. 1350037
Author(s):  
A. I. AHMADOV ◽  
E. A. KURAEV ◽  
YU. M. BYSTRITSKIY
Keyword(s):  
Pion Production ◽  
Spin Correlation ◽  
Proton Scattering ◽  
Correlation Effects ◽  
Pion Energy ◽  
Polarized Proton ◽  
Spectral Distributions ◽  
Spin Momentum

The process of two-pion production in the electron-polarized proton scattering is investigated. In the Weizsäcker–Williams approximation the differential spectral distributions and the spin-momentum correlations are considered. The spin correlation effects caused by ρ-meson widths are estimated to be of an order of several per cent. Both channels of the π+π- and π+π0 creation are considered. The effects of intermediate excited baryons are not considered. The spectral distributions on pion energy fractions in polarized and unpolarized cases are presented analytically and numerically.

scholarly journals Pseudo-hermitian andPT-symmetric quantum systems with energy-dependent potentials: Bound-state solutions and energy spectra

2017 ◽  
Vol 380 ◽  
pp. 78-92 ◽  
Author(s):  
Axel Schulze-Halberg ◽  
Pinaki Roy
Keyword(s):  
Bound State ◽  
Quantum Systems ◽  
Energy Spectra ◽  
Symmetric Quantum ◽  
Energy Dependent
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