scholarly journals Structure Functions of Hadrons in the QCD Effective Theory

1997 ◽  
Vol 50 (1) ◽  
pp. 139
Author(s):  
Takayuki Shigetani ◽  
Katsuhiko Suzuki ◽  
Hiroshi Toki
Keyword(s):  
Quark Distribution ◽  
High Energy ◽  
Structure Functions ◽  
Distribution Functions ◽  
Low Energy ◽  
Effective Theory ◽  
Spin Distribution ◽  
Diquark Model ◽  
Model Calculations ◽  
Diquark Correlation

We study the structure functions of hadrons with the low energy effective theory of QCD. We try to clarify a link between the low energy effective theory, where non-perturbative dynamics is essential, and the high energy deep inelastic scattering experiment. We calculate the leading twist matrix elements of the structure function at the low energy model scale within the effective theory. Calculated structure functions are taken to the high momentum scale with the help of the perturbative QCD, and compared with the experimental data. Through a comparison of the model calculations with the experiment, we discuss how the non-perturbative dynamics of the effective theory is reflected in the deep inelastic phenomena. We first evaluate the structure functions of the pseudoscalar mesons using the NJL model. The resulting structure functions show reasonable agreement with experiments. We then study the quark distribution functions of the nucleon using a covariant quark–diquark model. We calculate three leading twist distribution functions, the spin-independent f1(x), the longitudinal spin distribution g1(x), and the chiral-odd transversity spin distribution h1(x). The results for f1(x) and g1(x) turn out to be consistent with available experiments because of the strong spin-0 diquark correlation.

scholarly journals High-energy operator product expansion at sub-eikonal level

2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
Giovanni Antonio Chirilli
Keyword(s):  
Operator Product Expansion ◽  
Evolution Equations ◽  
Energy Operator ◽  
High Energy ◽  
Structure Functions ◽  
Distribution Functions ◽  
Impact Factors ◽  
Operator Product ◽  
The Impact ◽  
New Distribution

Abstract The high energy Operator Product Expansion for the product of two electromagnetic currents is extended to the sub-eikonal level in a rigorous way. I calculate the impact factors for polarized and unpolarized structure functions, define new distribution functions, and derive the evolution equations for unpolarized and polarized structure functions in the flavor singlet and non-singlet case.

scholarly journals The low-energy effective theory of axions and ALPs

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Martin Bauer ◽  
Matthias Neubert ◽  
Sophie Renner ◽  
Marvin Schnubel ◽  
Andrea Thamm
Keyword(s):  
High Energy ◽  
New Physics ◽  
Mass Scale ◽  
Low Energy ◽  
Effective Theory ◽  
Loop Order ◽  
Flavor Changing ◽  
Effective Lagrangian ◽  
Anomalous Dimensions ◽  
Pseudoscalar Mesons

Abstract Axions and axion-like particles (ALPs) are well-motivated low-energy relics of high-energy extensions of the Standard Model, which interact with the known particles through higher-dimensional operators suppressed by the mass scale Λ of the new-physics sector. Starting from the most general dimension-5 interactions, we discuss in detail the evolution of the ALP couplings from the new-physics scale to energies at and below the scale of electroweak symmetry breaking. We derive the relevant anomalous dimensions at two-loop order in gauge couplings and one-loop order in Yukawa interactions, carefully considering the treatment of a redundant operator involving an ALP coupling to the Higgs current. We account for one-loop (and partially two-loop) matching contributions at the weak scale, including in particular flavor-changing effects. The relations between different equivalent forms of the effective Lagrangian are discussed in detail. We also construct the effective chiral Lagrangian for an ALP interacting with photons and light pseudoscalar mesons, pointing out important differences with the corresponding Lagrangian for the QCD axion.

scholarly journals INFINITE STATISTICS, SYMMETRY BREAKING AND COMBINATORIAL HIERARCHY

2009 ◽  
Vol 24 (18) ◽  
pp. 1425-1435 ◽  
Author(s):  
VLADIMIR SHEVCHENKO
Keyword(s):  
Symmetry Breaking ◽  
Mechanical Model ◽  
Degrees Of Freedom ◽  
High Energy ◽  
Low Energy ◽  
Effective Theory ◽  
Quantum Mechanical ◽  
Hierarchy Problem ◽  
Induced Gravity ◽  
Large Numbers

The physics of symmetry breaking in theories with strongly interacting quanta obeying infinite (quantum Boltzmann) statistics known as quons is discussed. The picture of Bose/Fermi particles as low energy excitations over nontrivial quon condensate is advocated. Using induced gravity arguments, it is demonstrated that the Planck mass in such low energy effective theory can be factorially (in number of degrees of freedom) larger than its true ultraviolet cutoff. Thus, the assumption that statistics of relevant high energy excitations is neither Bose nor Fermi but infinite can remove the hierarchy problem without necessity to introduce any artificially large numbers. Quantum mechanical model illustrating this scenario is presented.

Analysis of positive pions obtained in d + C collisions at 4.2AGeV/c

2020 ◽  
Vol 29 (06) ◽  
pp. 2050041
Author(s):  
Imran Khan ◽  
Nabeela Feroz ◽  
Ali Zaman ◽  
Naseeb Ullah
Keyword(s):  
Boltzmann Distribution ◽  
High Energy ◽  
Distribution Functions ◽  
Transverse Mass ◽  
Inverse Slope ◽  
Model Calculations ◽  
Momentum Spectra ◽  
Inverse Slope Parameter ◽  
Transverse Momentum Spectra ◽  
High Energy Collisions

Temperature is an important and commonly used parameter among others to study properties of matter created during high energy collisions of nuclei. Experimental data from JINR and UrQMD (version 3.3p2) model simulations have been used to estimate temperature and other properties of positive pions in collisions of deuteron with carbon nuclei at incident momentum of 4.2[Formula: see text]GeV/[Formula: see text] in this paper. Transverse mass and transverse momentum spectra have been used to get inverse slope parameter/temperature of said particles, with the help of some fitting equations. These equations are referred as Hagedorn Thermodynamic and Boltzmann Distribution functions. Such functions or equations are used to describe particles spectra. Temperature of positive pions has been found to be equal to [Formula: see text] and [Formula: see text][Formula: see text]MeV in experimental and model, respectively, using Hagedorn function. Results from both experimental and model calculations have also been compared with each other and thus most reliable fitting function has been suggested. It is found that Hagedorn Thermodynamic function is the most reliable function to get pions’ temperature in said collision system at given momentum. Similarly, results obtained in this paper have been compared with results from other experiments in the world and worthy conclusions have been reached and reported.

scholarly journals POLARIZED STRUCTURE FUNCTIONS AND SPIN PHYSICS

2002 ◽  
Vol 17 (23) ◽  
pp. 3220-3238
Author(s):  
UTA STÖSSLEIN
Keyword(s):  
Parton Distribution ◽  
Spin Structure ◽  
High Energy ◽  
Structure Functions ◽  
Distribution Functions ◽  
High Energy Particle ◽  
Particle Interactions ◽  
Parton Distribution Functions ◽  
Spin Physics ◽  
Further Development

Recent progress in the field of spin physics of high energy particle interactions is reviewed with particular emphasis on the spin structure functions as measured in polarized deep inelastic lepton-nucleon scattering (DIS). New measurements are presented to obtain more direct information on the composition of the nucleon angular momentum, with results from semi-inclusive DIS accessing flavour-separated parton distribution functions (PDF) and with first data from hard exclusive reactions which may be interpreted in terms of recently developed generalizations of parton distribution functions (GPD). Finally, experimental prospects are outlined which will lead to a further development of the virtues of QCD phenomenology of the spin structure of the nucleon.

scholarly journals QCD PRECISION MEASUREMENTS AND STRUCTURE FUNCTION EXTRACTION AT A HIGH STATISTICS, HIGH ENERGY NEUTRINO SCATTERING EXPERIMENT: NuSOnG

2010 ◽  
Vol 25 (05) ◽  
pp. 909-949 ◽  
Author(s):  
T. ADAMS ◽  
P. BATRA ◽  
L. BUGEL ◽  
L. CAMILLERI ◽  
J. M. CONRAD ◽  
...  
Keyword(s):  
Standard Model ◽  
Energy Shift ◽  
High Energy ◽  
Structure Functions ◽  
Distribution Functions ◽  
Neutrino Beam ◽  
Model Parameters ◽  
Parton Distribution Functions ◽  
Neutrino Scattering ◽  
Scattering Experiment

We extend the physics case for a new high-energy, ultra-high statistics neutrino scattering experiment, NuSOnG (Neutrino Scattering On Glass) to address a variety of issues including precision QCD measurements, extraction of structure functions, and the derived Parton Distribution Functions (PDF's). This experiment uses a Tevatron-based neutrino beam to obtain a sample of Deep Inelastic Scattering (DIS) events which is over two orders of magnitude larger than past samples. We outline an innovative method for fitting the structure functions using a parametrized energy shift which yields reduced systematic uncertainties. High statistics measurements, in combination with improved systematics, will enable NuSOnG to perform discerning tests of fundamental Standard Model parameters as we search for deviations which may hint of "Beyond the Standard Model" physics.

scholarly journals Remark on the Kinematics of the One-Photon Production in Electron–Proton Scattering

1997 ◽  
Vol 12 (21) ◽  
pp. 1553-1559
Author(s):  
Wei Lu
Keyword(s):  
Phase Space ◽  
Deeply Virtual Compton Scattering ◽  
Quark Distribution ◽  
Photon Production ◽  
Distribution Functions ◽  
Proton Scattering ◽  
Diquark Model ◽  
Space Factor ◽  
The Cross ◽  
The One

We clarify some misleading mistakes in the literature about the phase space for the one-photon production in electron–proton scattering and present the correct overall phase space factor in the cross-section formula. Our conclusion is that the earlier diquark model predictions for the cross-sections of the one-photon production in electron–proton scattering are unreliable. Furthermore, we specify the phase space boundaries. In relation to the recent proposal to measure the off-diagonal quark distribution functions in the deeply virtual Compton scattering off the proton, we point out that the kinematics strongly disfavors such experiments.

scholarly journals Nonlinear corrections on the parametrization methods

2021 ◽  
Vol 81 (9) ◽  
Author(s):  
G. R. Boroun ◽  
B. Rezaei
Keyword(s):  
Cross Sections ◽  
Direct Method ◽  
Nonlinear Behavior ◽  
High Energy ◽  
Structure Functions ◽  
Distribution Functions ◽  
Reduced Cross Section ◽  
Color Dipole ◽  
Wide Range ◽  
Energy Processes

AbstractWe present nonlinear corrections (NLCs) to the distribution functions at low values of x and $$Q^{2}$$ Q 2 using the parametrization $$F_{2}(x,Q^{2})$$ F 2 ( x , Q 2 ) and $$F_{L}(x,Q^{2})$$ F L ( x , Q 2 ) . We use a direct method to extract nonlinear corrections to the ratio of structure functions and the reduced cross section in the next-to-next-to-leading order (NNLO) approximation with respect to the parametrization method (PM). Comparisons between the nonlinear results with the bounds in the color dipole model (CDM) and HERA data indicate the consistency of the nonlinear behavior of the gluon distribution function at low x and low $$Q^{2}$$ Q 2 . The nonlinear longitudinal structure functions are comparable with the H1 Collaboration data in a wide range of $$Q^{2}$$ Q 2 values. Consequently, the nonlinear corrections at NNLO approximation to the reduced cross sections at low and moderate $$Q^{2}$$ Q 2 values show good agreement with the HERA combined data. These results at low x and low $$Q^{2}$$ Q 2 can be applied to the LHeC region for analyses of ultra-high-energy processes.

scholarly journals ANALYZING POWERS IN INCLUSIVE PION PRODUCTION AT HIGH ENERGY AND THE NUCLEON SPIN STRUCTURE

1999 ◽  
Vol 14 (21) ◽  
pp. 1403-1412 ◽  
Author(s):  
K. SUZUKI ◽  
N. NAKAJIMA ◽  
H. TOKI ◽  
K.-I. KUBO
Keyword(s):  
Pion Production ◽  
Spin Asymmetry ◽  
High Energy ◽  
Distribution Functions ◽  
Proton Proton ◽  
Model Calculations ◽  
Proton Collisions ◽  
Analyzing Powers ◽  
Polarized Proton ◽  
Proton Proton Collisions

Analyzing powers in inclusive pion production in high energy transversely polarized proton–proton collisions are studied theoretically in the framework of the quark recombination model. Calculations by assuming the SU(6) spin-flavor symmetry for the nucleon structure disagree with the experiments. We solve this difficulty by taking into account the realistic spin distribution functions of the nucleon, which differs from the SU(6) expectation at large x, with a perturbative QCD constraint on the ratio of the unpolarized valence distributions, u/d→5 as x→ 1. We also discuss the kaon spin asymmetry and find AN(K+)=-AN(K0) in the polarized proton–proton collisions at large x F .

EXTRACTING GLUON FRAGMENTATION FUNCTIONS IN HADRON-HADRON COLLISIONS

1989 ◽  
Vol 04 (06) ◽  
pp. 1485-1491
Author(s):  
DONGSHENG DU ◽  
YUZHEN GE ◽  
MA LUO
Keyword(s):  
Valence Quark ◽  
Quark Distribution ◽  
Structure Functions ◽  
Distribution Functions ◽  
Pp Collisions ◽  
Fragmentation Functions ◽  
Gluon Fragmentation ◽  
Better Than

Two methods for extracting gluon fragmentation functions in π±p, [Formula: see text] and pp collisions are proposed. The only inputs are valence-quark distribution functions which we know much better than other structure functions and fragmentation functions. So better extraction of gluon fragmentation functions can be obtained.

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