For theoretically consistent determination of $α_s$ from jet rates in deep inelastic scattering the dependence on $α_s$ of parton distribution functions is in principle as important as that of hard scattering cross-sections. For the kinematical region accessible at HERA we investigate in detail numerical importance of these two sources of the $α_s$ dependence of jet rates.
Three different kinds of scaling are observed in a toy model of turbulence (“GOY”). The first has a multifractal spectrum of exponents. The second is a simple static selfsimilarity solution. The third phase is dynamic but has simple scaling. This last previously unreported equipartition behavior is discussed. It is drastically different from the other two in terms of its scaling exponent(s) and emerges when the energy flux on the boundaries vanishes (no dissipation and no forcing).
A future linear collider such as TESLA may be able to run on the Z0 resonance with very high luminosity and polarised electron and positron beams. The possibilities of measuring electroweak quantities with high precision are investigated. Huge improvements with respect to the present precision can be expected, especially for the asymmetries A_LR and A_b where beam polarisation can be exploited. The very large sample of Z to bbbar events also allows studies of various CP-violating b decays. The precision achievable on the CKM unitarity triangle angles is comparable to experiments at b factories and future hadron colliders.
We show that taking into account the interplay between perturbative and non-perturbative effects, the power-suppressed shift to the broadening distributions becomes B dependent, and the non-perturbative contribution to the mean values becomes proportional to \(1/(Q\sqrt{\alpha_s(Q)})\). The new theoretical treatment greatly improves the consistency of the phenomenology with the notion of the universality of confinement effects in jet shapes.
The weights and representation matrices of the vector and the spinor representation of the Lie algebra SO(9) are introduced in the quantum mechanical language. Tensor product decompositions of any two of them are explicitly shown by using an algebraic method of quantum mechanics. Similar decompositions are finally achieved for a coupled tensor operator in the picture of Schwinger’s bosonic oscillators.
A quantitative model describing the large magnetostrain effect observed in several ferromagnetic shape memory alloys such as Ni2MnGa is briefly reported. The paper contains an exact thermodynamic consideration of the mechanical and magnetic properties of similar types of materials. As a result, the basic mechanical state equation including magnetic field effect is directly derived from a general Maxwell relation. It is shown that the magnetic field induced deformation effect is directly connected with the strain dependence of magnetization. A simple model of magnetization and its dependence on the strain is considered and applied to explain the results of experimental study of large magnetostrain effects in Ni2MnGa.
We analyze the time evolution of simple nuclear rotational wave packets (WP) called circular, linear or elliptic, depending on squeezing parameter η, assuming that E=ħω0I(I+ 1). The scenario of fractional revivals found by Averbukh and Perelman is adapted to symmetric WP and compared to that which holds for asymmetric WP. In both cases various shapes are identified under these lines in particular many cases of cloning. “Mutants” WP are found most often. Finally the time evolution of a WP formed by Coulomb excitation on 238U and calculated by semiclassical theory is also presented.
Moment analysis of global multiplicity distributions previously done for e + e − and hh processes is applied to hA and AA collisions. Oscillations of cumulants as functions of their rank are found in all processes for which experimental data are available. A similar oscillation pattern is found in the dual parton model and quark-gluon string models but not in the phenomenological fits such as modified negative binomial distributions. The zeros of the truncated generating function move closer and closer to the unity circle in the complex z-plane when the complexity of the collision increases.
The modern formulation of exclusive reactions within Quantum Chromodynamics is reviewed, the emphasis being placed on the pivotal ideas and methods pertaining to perturbative and non-perturbative topics. Specific problems, related to scale locality, infrared safety, gluonic radiative corrections (Sudakov effects), and the role of hadronic size effects (intrinsic transverse momentum), are studied. These issues are more precisely analyzed in terms of the essential mechanisms of momentum transfer to a hadron while remaining intact. Different factorization schemes are considered and the conceptual lacunas are pointed out. The quite technical subject of renormalization-group evolution is given a detailed account. By combining analytical and numerical algorithms, the one-gluon exchange nucleon evolution equation is diagonalized and next-to-leading eigenfunctions are calculated in terms of Appell polynomials. The corresponding anomalous dimensions of trilinear quark operators are found to form a degenerate system whose envelope shows logarithmic large-order behavior. Selected applications of this framework are presented, focusing on the helicity-conserving elastic form factors of the pion and the nucleon. The theoretical constraints imposed by QCD sum rules on the moments of nucleon distribution amplitudes are used to determine a whole spectrum of optional solutions. They organize themselves along an ``orbit'' characterized by a striking scaling relation between the form-factor ratio $R=|G_{\rm M}^{\rm n}|/G_{\rm M}^{\rm p}$ and the projection coefficient $B_{4}$ on to the corresponding eigensolution. The main reasons for the failure of the present theoretical predictions to match the experimental data are discussed and workable explanations are sketched.
The issue of the form that the energy tensor of the electromagnetic field should be given in matter is reconsidered, and the neat derivation of Abraham’s tensor once provided by W. Gordon is recollected. In order to extend to the high frequency domain the experimental evidence gathered up to now in favour of Abraham’s tensor, a method for detecting the Abraham’s force supposedly exerted by light on a transparent, homogeneous medium is outlined. It avails of the Fresnel-Fizeau effect associated with the motion of matter that should be caused by the above mentioned force.
The contribution of hadronic vacuum polarization to the Lamb shift in muonic hydrogen is evaluated with the account of modern experimental data on the cross section of e+e− annihilation into hadrons. The numerical value of this contribution to the (2P-2S) shift in muonic hydrogen is equal to 10.95 µeV.
We present one- and two-jet inclusive cross sections for γ*γ scattering and virtual photoproduction in ep collisions. The hard cross sections are calculated in next-to-leading order QCD. Soft and collinear singularities are extracted using the phase-space-slicing method. The initial state singularity of the virtual photon depends logarithmically its’ virtuality. This logarithm is large and has to be absorbed into the parton distribution function of the virtual photon. We define for this purpose an \({\overline MS}\) factorization scheme similar to the real photon case. We numerically study the dependence of the inclusive cross sections on the transverse energies and rapidities of the outgoing jets and on the photon virtuality. The ratio of the resolved to the direct cross section in ep collisions is compared to ZEUS data.
We present a study of parity (P) violating contributions to the eigenenergies of stationary systems containing atoms in spatially inhomogeneous external electric fields. In this context the subtle interplay of P-violation and time reversal (T) invariance plays an important role. If the entire field configuration is chosen to exhibit chirality the energies are in general shifted by pseudoscalar contributions which change sign under a planar reflection of the field. In part I we consider sudden variations of the fields and calculate P-violating energy shifts using perturbation theory. In part II the adiabatic case will be treated and the connection to geometrical (Berry-) phases will be elucidated. To calculate the effects we use the standard model of elementary particle physics where the P-odd interaction arises through the exchange of Z-bosons between the quarks in the nucleus and the atomic electrons. We consider in detail hydrogen-like systems in unstable levels of principal quantum number n = 2. We study atoms with vanishing nuclear spin like \(_{1}^{1}{\rm He}^{+}\) and with nuclear spin I = 1/2 like \(_{1}^{1}{\rm H}\). The nominal order of P-violating effects is 10−5...10−9 Hz which is determined by the mixing of the 2S1/2 and 2P1/2 states. However we point out that with certain configurations of the external fields, it is possible to enhance the P-violating energy shifts dramatically! Instead of energy shifts linear in the P-violation parameters we get then shifts proportional to the square root of these parameters. Numerically we find such energy shifts which only appear for unstable states to be of order 10−5...1 Hz. Under a reversal of the handedness of the external field configuration these P-violating shifts get multiplied by a phase factor i, i.e. the shifts in the real and imaginary part of the complex eigenenergies are exchanged. Application of our technique to hydrogen-like atoms with a nucleus of spin I = 1/2 yields P-violating energy shifts which are very sensitive to the nuclear spin dependent P-odd force, which receives a rather large contribution from the polarized strange quark density in polarized nuclei. Thus, a measurement of these energy shifts could provide an important tool to elucidate nuclear properties connected to the so called “spin crisis”. We also present a method for treating degenerate perturbation theory which combines advantages of both, Kato’s and Bloch’s methods.
The ``orthodox theory'' of a single electron double junction is dealt with. It is shown that the stationary solution of the underlying master equation allows the construction of any time-dependent solution in terms of orthogonal polynomials. The approach pays off if the stationary solution becomes simple. Two special cases are considered. We use the time-dependent solution to calculate the current noise in these cases.
It is shown that the energy deposition pattern in deep calorimeters could be the spectacular and unconventional signature of different kinds of stable and unstable strangelets. As an example the detection method of strongly penetrating objects, such as strangelets possibly produced in the baryon-rich environment formed in central Pb-Pb collisions at LHC energies, is described.
We present a study of correlations between D and D mesons produced in 500 GeV/ c π − -nucleon interactions, based on data from experiment E791 at Fermilab. We have fully reconstructed 791 ± 44 charm meson pairs to study correlations between the transverse and longitudinal momenta of the two D mesons and the relative production rates for different types of D meson pairs. We see slight correlations between the longitudinal momenta of the D and the D̅ , and significant correlations between the azimuthal angle of the D and the D̅ . The experimental distributions are compared to a next-to-leading-order QCD calculation and to predictions of the P YTHIA /J ETSET Monte Carlo event generator. We observe less correlation between transverse momenta and different correlations between longitudinal momenta than these models predict for the default values of the model parameters. Better agreement between data and theory might be achieved by tuning the model parameters or by adding higher order perturbative terms, thus contributing to a better understanding of charm production. The relative production rates for the four sets of charm pairs, D^0D^0, D^0 D^-, D^+D^0, D^+ D^- as calculated in the P YTHIA /J ETSET event generator with the default parameters, agree with data as far as the relative ordering, but predict too many D^+ D^0 pairs and too few D^+ D^- pairs.
We consider the possible role played by the anomaly cancellation mechanism in the evaluation of the radiatively induced Chern-Simons (CS) term, arising from the Lorentz and CPT non-invariant fermionic sector, of an extended version of QED. We explicit evaluate the most general mathematical structure associated to the AVV triangle amplitude, closely related to the one involved in the CS term evaluation, using for this purposes an alternative calculational strategy to handle divergences in QFT’s. We show that the requirement of consistency with the choices made in the construction of the Standard Model’s renormalizability, in the evaluation of the AVV Green function, leave no room for a nonvanishing radiatively induced CS term, independently of the regularization prescription or equivalent philosophy adopted, in accordance with what was previously conjectured by other authors.
Results on measurements of the proton structure function from the two HERA experiments H1 and ZEUS in 1994 show that perturbative QCD (pQCD) allows to describe the observed rapid rise of with decreasing x down to Q 2 = 1.5GeV 2 . Whereas the pQCD region exhibits a strong rise of σ γ* p tot with increasing W 2 , the total cross-section for real photon-proton scattering σ γ p tot shows only a modest rise with W 2 . The proton structure function F 2 and the total virtual photon-proton (γ* p ) cross-section σ γ* p tot have been measured in inelastic neutral current scattering, e + p → e + X , at HERA in the previously unexplored transition region of non-perturbative to perturbative QCD at low Q 2 . To study this kinematic region, a small electromagnetic Beam Pipe Calorimeter (BPC) has been designed, constructed and installed in the ZEUS experiment in 1995. The accuracy of the measurement of F 2 in this kinematic region relies mainly on a precise energy calibration and detector alignment. An energy calibration with a precision of 0.5% and a detector alignment of 0.5mm have been achieved. Results on a measurement of F 2 and σ γ p tot are obtained for 0.11 ≤ Q 2 ≤ 0.65 GeV 2 and 1.7 ċ 10 −6 ≤ x ≤ 6.0 ċ 10 −5 , corresponding to a range in the γ* p center-of-mass energy of 104 ≤ W ≤ 251 GeV. The results on F 2 and σ γ p tot indicate a smooth transition between the pQCD region and the photoproduction region. A detailed phenomenological analysis as well as a QCD analysis has been carried out to investigate the limitations of a non-perturbative as well as a perturbative QCD description.
We discuss how the evasive Odderon signal can be enhanced by final state interactions. We suggest the charge asymmetry of pion spectra in diffractive pi+pi- photoproduction as a promising signature of the Odderon exchange.
