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This is the report of the QCD working group at WHEPP-6. Discussions and work on heavy ion collisions, polarized scattering, and collider phenomenology are reported.

Abstract: This is the report of the QCD working sub-group at WHEPP-8 which was part of the QCD and QGP working group. Discussion and work on some aspects of resummation and parton distribution are reported.

Abstract: This is the report of neutrino and astroparticle physics working group at WHEPP-8. We present the discussions carried out during the workshop on selected topics in the above fields and also indicate progress made subsequently. The neutrino physics subgroup studied the possibilities of constraining neutrino masses, mixing and CPT violation in lepton sector from future experiments. Neutrino mass models in the context of Abelian horizontal symmetries, warped extra dimensions and in the presence of triplet Higgs were studied. Effect of threshold corrections on radiative magnification of mixing angles was investigated. The astroparticle physics subgroup focused on how various particle physics inputs affect the CMBR fluctuation spectrum, and on brane cosmology. This report also contains an introduction on how to use the publicly available code CMBFAST to calculate the CMBR fluctuations.

Abstract: We present some physics possibilities with an iron calorimeter detector (ICAL) and a status report on the feasibility study to construct such a detector at a future possible India-based Neutrino Observatory (INO). This talk was given at the workshop on high energy physics phenomenology, WHEPP-8, in Jan. 2004, at IIT Bombay.

We have identified some important and worthwhile physics opportunities with a possible neutrino detector located in India. Particular emphasis is placed on the geographical advantage with a stress on the complimentary aspects with respect to other neutrino detectors already in operation.

This talk gives a summary of recent results in deep inelastic lepton hadron scattering. This includes structure functions from inclusive measurements as well as fragmentation in semi-inclusive processes, mainly with respect to data from colliders such as HERA at DESY, and their associated phenomenology.

We discuss thex-dependence of the spin dependent structure function data currently available for proton, neutron and deuteron targets, with emphasis on the non-singlet sector. We pinpoint the sources of deviation of the data fromtheoretical expectations based, in particular, on the Bjorken sum rule. We conclude that apparent discrepancies can be reconciled so that the data are consistent with theoryprovided the large-x limit is properly defined.

Following recent interest in the subject of polarisation phenomena, we discuss the cross-sections and polarisation asymmetry in 2-jet production in polarised proton-polarised proton ( ) scattering. We set up a complete set of parametrisations for the proton spin-dependent parton densities and use them to demonstrate that this cross-section is dominated by gluonic terms. Hence, a measurement of the asymmetry in such processes will provide information on the gluon spin-dependent density. We further show that a factorisation of the hadronic cross-section a la Combridge and Maxwell's work in unpolarised 2-jet production also applies to the spin-dependent case. Hence, the cross-section can be written in terms of a genericpolarised parton density, which can then be measured in the process.

We propose a set of polarised-beam polarisedtarget experiments to determine the complete set of spin dependent parton densities. The polarised valence quark densities are determined through semi-inclusive hadroproduction in polarised muon-proton collisions. This, together with present data then fixes the polarised sea quark densities. Polarised gluon densities are measurable through asymmetries in large,pT direct photon production in polarisedp-p collisions. An independent measurement of polarised sea quark densities comes from direct double photon production in polarisedp-p collisions at rapidities close to zero. We illustrate these results with numerical estimates.

We investigate spin asymmetries in highpT photon and dimuon production and show that the spin dependent gluon density can be extracted reliably frompp collisions with these final states. The statement remains true even when the balancing jet is not observed. Hence fixed target experiments can be used to measure the spin dependent gluon density. We also compute the asymmetries in collisions, and show that the EMC measurement of the spin structure function can be verified and the spin dependent gluon density can be extracted from these experiments.

We consider a typical hard scattering process in a heat bath of photons and electrons at temperature,T, in finite temperature QED. We show that the infrared pieces of both the real and virtual parts of the cross section factorise; these can be exponentiated and cancel between each other to all orders in perturbation theory. Hence the Bloch–Nordsieck theorem remains valid for such processes at non-zero temperature as well. We use the technique of Grammer and Yennie to give a prescription for the extraction of the infrared divergent parts and for the form of the finite remainder. Symmetry arguments are used to show the finiteness of new terms arising in theT≠0 part of the computation.

Detailed results of an experiment, looking for a short-lived neutral particle decaying by ane+e−pair in the decay of the 3.68 MeV (3/2) state in13C, whose decay is predominantly M1, are presented. An upper limit of 7 × 10−5has been placed on the branching ratio for decay through such a particle with a mass in the range 1.7 to 1.9 MeV/c2. This leads to an upper limit of 10−6for the coupling of such a particle to nucleons. Such a limit rules out the explanation of thee+ande−peaks recently observed in heavy ion collisions, as due to the decay of a neutral particle.

Abstract: This talk discusses the current understanding in some aspects of polarised lepton-nucleon deep inelastic scattering. The first section focuses on the non-singlet part of available spin dependent structure function data. The results, though consistent with theoretical predictions in this sector, are extremely sensitive to extrapolation of the data to thex→1 region and seem to indicate that the quarksdo carry a very small fraction of the nucleon spin. We then review the formalism of DIS processes with emphasis on the gluon sector.