Twist – 4 quark – quark correlations in the pion from the instanton vacuum

نویسندگان

  • Nam – Young Lee
  • K. Goeke
  • C. Weiss
چکیده

The second moment of the isospin–2 structure function of the pion, F π+ 2 +F π− 2 −2F π 0 2 , is determined by the pion matrix element of a four–quark operator of twist 4. This isospin–2 operator cannot mix with lower–dimensional operators, and thus provides a clean probe of the quark–quark correlations in the pion. We calculate the matrix element in the effective chiral theory based on the instanton vacuum. We find a surprisingly small value, A I=2 ≈ 0.14 F 2 π = (35 MeV) 2 , in good agreement with recent lattice results. The order of magnitude of the result is explained by the diluteness of the instanton medium, ¯ ρ/ ¯ R ≈ 1/3.

برای دانلود رایگان متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

Quark distribution in the pion within the instanton liquid model

The leading-twist valence-quark distribution function in the pion is obtained at a low normalization scale of an order of the inverse average size of an instanton ρc. The momentum dependent quark mass and the quark-pion vertex are constructed in the framework of the instanton liquid model, using a gauge invariant approach. The parameters of instanton vacuum, the effective instanton radius and q...

متن کامل

Quark Distribution Function in Pion within Instanton Liquid Model

We calculate the leading-twist valence-quark distribution function in the pion at a low normalization scale of an order of the inverse average size of an instanton ρc. The quark-pion dynamics and the construction of the quark-pion vertex function are considered in the framework of the instanton liquid model. The parameters of instanton vacuum, the effective instanton radius and quark mass, are ...

متن کامل

Leading-twist pion and kaon distribution amplitudes in the gauge-invariant nonlocal chiral quark model from the instanton vacuum

We investigate the leading-twist light-cone distribution amplitudes for the pion and kaon based on the gauge-invariant nonlocal chiral quark model from the instanton vacuum in the presence of external axial-vector currents. We find that the nonlocal contribution from the gauge invariance has much effects on the pion distribution amplitudes, while it changes mildly the kaon ones. We also study t...

متن کامل

Pion and photon light–cone wave functions from the instanton vacuum

The leading–twist wave functions of the pion and the photon at a low normalization point are calculated in the effective low–energy theory derived from the instanton vacuum. The pion wave function is found to be close to the asymptotic one, consistent with the recent CLEO measurements. The photon wave function is non-zero at the endpoints. This different behavior is a consequence of the momentu...

متن کامل

Off - diagonal quark distribution functions of the pion within an effective single instanton approximation

We develop a relativistic quark model for hadron structure which, incorporates the non-trivial structure of the vacuum of Quantum Chromodynamics as modelled by instantons, and is defined taking properly into account gauge invariance. Hadrons are boundstates of quarks and the strong quark-hadron vertices are determined from an instanton induced effective lagrangian. The parameters of the model, ...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

عنوان ژورنال:

دوره   شماره 

صفحات  -

تاریخ انتشار 2000