2 research outputs found
The use of RPC in the ARGO-YBJ Project
We present the ARGO-YBJ experiment, a full coverage detector placed at high altitude (∼4300 m a.s.l.) that exploits the RPC technique. Results of a test experiment performed at Yanbajing site, with a full coverage RPC carpet of 50 m2 are also presented
Medium modification of the shape of small-radius jets in central Pb-Pb collisions at root s(NN)=2:76 TeV
Abstract: We present the measurement of a new set of jet shape observables for track- based jets in central Pb-Pb collisions at √sNN = 2.76 TeV. The set of jet shapes includes the first radial moment or angularity, g; the momentum dispersion, pTD; and the differ- ence between the leading and sub-leading constituent track transverse momentum, LeSub.
These observables provide complementary information on the jet fragmentation and can constrain different aspects of the theoretical description of jet-medium interactions. The jet shapes were measured for a small resolution parameter R = 0.2 and were fully corrected to
particle level. The observed jet shape modifications indicate that in-medium fragmentation
is harder and more collimated than vacuum fragmentation as obtained by PYTHIA cal- culations, which were validated with the measurements of the jet shapes in proton-proton
collisions at √s = 7 TeV. The comparison of the measured distributions to templates for
quark and gluon-initiated jets indicates that in-medium fragmentation resembles that of quark jets in vacuum. We further argue that the observed modifications are not consistent with a totally coherent energy loss picture where the jet loses energy as a single colour charge, suggesting that the medium resolves the jet structure at the angular scales probed
by our measurements (R = 0.2). Furthermore, we observe that small-R jets can help to
isolate purely energy loss effects from other effects that contribute to the modifications of the jet shower in medium such as the correlated background or medium response