Jets in High-q2 Dis at Hera

The shapes of jets with transverse energies, E jet T , up to 45 GeV produced in neutral-current(NC) and charged-current (CC) deep inelastic e + p scattering (DIS) at Q 2 > 100 GeV 2 have been measured with the ZEUS detector at HERA. Jets are identiied using a cone algorithm in the ? ' plane with a cone radius of one unit. The jets become narrower as E jet T increases. The jet shapes in NC and CC DIS are found to be very similar. The jet shapes in DIS are observed to be similar to those in e + e ? interactions and narrower than those in pp collisions for comparable E jet T. Measurements of diierential jet cross sections in NC DIS at Q 2 > 125 GeV 2 are presented as a function of jet and E jet T and compared with Monte Carlo predictions. 1 Deenition of the Jet Shape The internal structure of a jet is expected to depend mainly on the type of primary parton, quark or gluon, from which it originated and to a lesser extent on the particular hard scattering process. The structure of the jets depends, to some extent, upon the algorithm used in the jet search. An iterative cone algorithm in ? space 1;2 , with a cone radius R equal to one unit, is used to reconstruct jets from the energy depositions in the calorimeter cells. Jets with transverse energies E jet T > 14 GeV and pseudorapidities (jet) in the range ?1 < jet < 2 are selected. For cone jet algorithms a useful representation of the jet's internal structure is given by the jet shape 3. The diierential jet shape is deened as the average fraction of the jet's transverse energy that lies inside an annulus in the ?' plane of inner (outer) radius r ?r=2 (r+r=2) concentric with the jet deening cone: (r) = 1 N jets