Polarized 3 parton production in inclusive DIS at small x

Azimuthal angular correlations between produced hadrons/jets in high energy collisions are a sensitive probe of the dynamics of QCD at small x. Here we derive the triple differential cross section for inclusive production of 3 polarized partons in DIS at small x using the spinor helicity formalism. The target proton or nucleus is described using the Color Glass Condensate (CGC) formalism. The resulting expressions are used to study azimuthal angular correlations between produced partons in order to probe the gluon structure of the target hadron or nucleus. Our analytic expressions can also be used to calculate the real part of the Next to Leading Order (NLO) corrections to di-hadron production in DIS by integrating out one of the three final state partons.Comment: 5 pages, 6 figures; version accepted for publication in Physics Letters

Shadowing of gluons in perturbative QCD: A comparison of different models

We investigate the different perturbative QCD-based models for nuclear shadowing of gluons. We show that in the kinematic region appropriate to RHIC experiment, all models give similar estimates for the magnitude of gluon shadowing. At scales relevant to LHC, there is a sizable difference between predictions of the different models.Comment: 11 pages, 4 figure

From RHIC to EIC: Nuclear Structure Functions

We study the nuclear structure function $F_2^A$ and its logarithmic derivative in the high energy limit (small $x$ region) using the Color Glass Condensate formalism. In this limit the structure function $F_2$ depends on the quark anti-quark dipole-target scattering cross section $N_F (x_{bj}, r_t, b_t)$. The same dipole cross section appears in single hadron and hadron-photon production cross sections in the forward rapidity region in deuteron (proton)-nucleus collisions at high energy, i.e. at RHIC and LHC. We use a parameterization of the dipole cross section, which has successfully been used to describe the deuteron-gold data at RHIC, to compute the nuclear structure function $F_2^A$ and its log $Q^2$ derivative (which is related to gluon distribution function in the double log limit). We provide a quantitative estimate of the nuclear shadowing of $F_2^A$ and the gluon distribution function in the kinematic region relevant to a future Electron-Ion Collider.Comment: 13 pages, 6 figure

Characterization and Performance Evaluation of Mono-grain and Bi-modal PCD Grade in Machining of MMC

AbstractThe aim of this investigation is to study the influence of different parameters such as grain size and cobalt content on the tool performance in the machining of metal matrix composite (MMC) using different polycrystalline diamond (PCD) tools. The experimental tests were conducted with four different PCD grades in dry the milling of Aluminium-Silicon carbide (Al-SiC) composite containing 20% wt of SiC as a workpiece material. The SEM study shows that PCD grades I and II have a bimodal grain size distribution. Rietveld refinement of the XRD spectra for these grades indicates that grade I contains larger amount of Co compared to grade II. The difference in performance between these grades can be explained by the Co content. PCD grade III is a coarse grain grade while grade IV is a fine grain grade. An XRD analysis shows that the main difference between the mono- grain and bimodal grain PCD is the presence of WC in the mono-grain grades which is believed to be added to the raw material of PCD as a grain growth inhibitor. In the XRD pattern for the bimodal grades the peaks in the WC phase are completely absent. The results indicate that the tool performance in terms of wear development is influenced by grain size distribution, cobalt content and the presence of WC; where the abrasive wear is the main wear mechanism which determines the tool life of the diamond grades in milling MMC. The results also indicates that the MMC can be machined with any diamond grade at the low range of cutting speed (≤ 400 m/min) while at a higher range of cutting speed (> 400 m/min) the selection of the diamond grade should be based on the chemical composition and grain size distribution. The presence of grain growth inhibitor also has a significant effect on the tool performance in machining MMC at cutting speeds above 400 m/min

Non-Gaussian Correlations in the McLerran-Venugopalan Model

We argue that the statistical weight function W[rho] appearing in the McLerran-Venugopalan model of a large nucleus is intrinsically non-Gaussian, even if we neglect quantum corrections. Based on the picture where the nucleus of radius R consists of a collection of color-neutral nucleons, each of radius a<<R, we show that to leading order in alpha_s and a/R only the Gaussian part of W[rho] enters into the final expression for the gluon number density. Thus, the existing results in the literature which assume a Gaussian weight remain valid.Comment: 21 pages with 4 figures (revtex

More Remarks on High Energy Evolution

We discuss several issues related to recent work on high energy evolution. In particular we show that the Hilbert space for action of the operator of the evolution can be conveniently defined by the space of weight functional introduced recently in \cite{kl4}. These weight functionals automatically implement the correct properties of the charge density correlators, thus eliminating the need in explicit introduction of the Wess Zumino term. We also discuss various aspects of Dense Dilute Duality in the toy dipole model.Comment: 20 pages, 1 figur

The Wilson renormalization group for low x physics: towards the high density regime

We continue the study of the effective action for low $x$ physics based on a Wilson renormalization group approach. We express the full nonlinear renormalization group equation in terms of the average value and the average fluctuation of extra color charge density generated by integrating out gluons with intermediate values of $x$. This form clearly exhibits the nature of the phenomena driving the evolution and should serve as the basis of the analysis of saturation effects at high gluon density at small $x$.Comment: 14 pages, late

Chiral dynamics and the growth of the nucleon's gluonic transverse size at small x

We study the distribution of gluons in transverse space in the nucleon at moderately small x (~10^{-2}). At large transverse distances (impact parameters) the gluon density is generated by the 'pion cloud' of the nucleon, and can be calculated in terms of the gluon density in the pion. We investigate the large-distance behavior in two different approaches to chiral dynamics: i) phenomenological soft-pion exchange, ii) the large-N_c picture of the nucleon as a classical soliton of the pion field, which corresponds to degenerate N and Delta states. The large-distance contributions from the 'pion cloud' cause a \~20% increase in the overall transverse size of the nucleon if x drops significantly below M_pi/M_N. This is in qualitative agreement with the observed increase of the slope of the t-dependence of the J/psi photoproduction cross section at HERA compared to fixed-target energies. We argue that the glue in the pion cloud could be probed directly in hard electroproduction processes accompanied by 'pion knockout', gamma^* + N -> gamma (or rho, J/psi) + pi + N', where the transverse momentum of the emitted pion is large while that of the outgoing nucleon is restricted to values of order M_pi.Comment: 20 pages, revtex4, 10 eps figure

The Iancu-Mueller factorization and high energy asymptotic behaviour

We show that the Iancu-Mueller factorization has a simple interpretation in the Reggeon - like technique based on the BFKL Pomeron. The formula for calculating the high energy asymptotic behaviour for the colour dipole-dipole amplitude is proposed which suggests a procedure to calculate this amplitude through the solution to the Balitsky-Kovchegov non-linear equation. We confirm the Iancu - Mueller result that a specific set of enhanced diagrams is responsible for the high energy behaviour for fixed QCD coupling. However, it is argued that in the case of running QCD coupling, this asymptotic behaviour originates from the Balitsky-Kovchegov non-linear equation. A new solution to the non-linear equation is found which leads to a different asymptotic behaviour of the scattering amplitude even for fixed QCD coupling..Comment: 27 pages, 9 figuure