Unifying the Fixed Order Evolution of Fragmentation Functions with the Modified Leading Logarithm Approximation

An approach which unifies the Double Logarithmic Approximation at small x and the leading order DGLAP evolution of fragmentation functions at large x is presented. This approach reproduces exactly the Modified Leading Logarithm Approximation, but is more complete due to the degrees of freedom given to the quark sector and the inclusion of the fixed order terms. We find that data from the largest x values to the peak region can be better fitted than with other approaches

Perturbative QCD Approach to Multiparticle Production

In this review we discuss the analytical perturbative approach, based on perturbative QCD and Local Parton Hadron Duality (LPHD), and its application to multiparticle production in jets in the semisoft region. Analytical formulae are presented for various observables within the accuracy of the Modified Leading Logarithmic Approximation (MLLA), i.e. with terms of relative order $\sqrt{\alpha_s}$ taken into account systematically, and in some cases with even higher accuracy. These predictions are confronted with existing experimental data. Many details of the perturbative approach to multiple hadroproduction have been consolidated in recent years, and the overall picture is remarkably healthy. The prospects of future studies of the semisoft jet physics are also discussed.Comment: LaTex, 153 pages, 54 figures available from the authors; to be publ. by Int. Journal of Modern Physics

Quantitative tests of mixed crystal exciton theory. II. Energy denominator study of naphthalene 1B2u resonance pairs

A spectroscopic absorption study is presented of 1‐D1C10H7, 2‐D1C10H7, and 1,4‐D2C10H7 resonance pairs in C10D8, over a concentration range of 0.009% to 5% mole, at 2 °K, with a resolution of 0.5 cm−1. The resulting structure is interpreted in terms of the pairwise exciton exchange interactions, M1/2(a+b), Ma, Mb, Mc, Ma+c, and M1/2(a+b)+c. The energy denominator dependence is interpreted in terms of both exciton quasiresonance and exciton superexchange. The three parameter sets derived by Hong and Kopelman to fit earlier data on neat and isotopic mixed crystals are corroborated by this study, as they were in our previous study on monomers (I). However, it was not possible to narrow down completely the choice of parameters. A discussion is given on the feasibility of deriving a unique dispersion relation (and Green’s function) for the first naphthalene singlet exciton and on its likely precision.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70131/2/JCPSA6-66-4-1599-1.pd

A Monte Carlo Study on the Dynamical Fluctuations Inside Quark and Antiquark Jets

The dynamical fluctuations inside the quark and antiquark jets are studied using Monte Carlo method. Quark and antiquark jets are identified from the 2-jet events in e+e- collisions at 91.2 GeV by checking them at parton level. It is found that transition point exists inside both of these two kinds of jets. At this point the jets are circular in the transverse plane with respect to the property of dynamical fluctuations. The results are consistent with the fact that the third jet (gluon jet) was historically first discovered in e+e- collisions in the energy region 17-30 GeV.Comment: 9 pages, 4 figure

Novel Scaling Behavior for the Multiplicity Distribution under Second-Order Quark-Hadron Phase Transition

Deviation of the multiplicity distribution $P_q$ in small bin from its Poisson counterpart $p_q$ is studied within the Ginzburg-Landau description for second-order quark-hadron phase transition. Dynamical factor $d_q\equiv P_q/p_q$ for the distribution and ratio $D_q\equiv d_q/d_1$ are defined, and novel scaling behaviors between $D_q$ are found which can be used to detect the formation of quark-gluon plasma. The study of $d_q$ and $D_q$ is also very interesting for other multiparticle production processes without phase transition.Comment: 4 pages in revtex, 5 figures in eps format, will be appeared in Phys. Rev.