Measurement of diffractive production of D∗±(2010) mesons in deep-inelastic scattering at HERA

Abstract

Diffractive production of D * ± (2010) mesons in deep inelastic scattering has been measured with the ZEUS detector at HERA using an integrated luminosity of 44.3 pb −1 . Diffractive charm production is identified by the presence of a large rapidity gap in the final state of events in which a D * ± (2010) meson is reconstructed in the decay channel. Differential cross sections when compared with theoretical predictions indicate the importance of gluons in such diffractive interactions.

Measurement of charm fragmentation fractions in photoproduction at HERA

“…The measurements are compared to previous HERA results [1][2][3][4] and to the combined fragmentation fractions for charm production in e + e − annihilations compiled previously [16] and updated [17,50] with the 2010 branching-ratio values [51]. This comparison is also shown in figure 6.…”

“…The new measurement benefits also from the ZEUS microvertex detector (MVD), which made it possible to identify the secondary decay vertices of the charm ground states and thereby to suppress background significantly. The new results are compared to the previous ZEUS measurement [1] in photoproduction, other HERA results from H1 [2] and ZEUS [3,4] in deep inelastic scattering, and to results from experiments at the e + e − storage rings CLEO [5,6], ARGUS [7][8][9] and the LEP experiments [10][11][12][13][14][15]. A summary is given in [16], with an update to 2010 branching ratios [17].…”

“…The numbers of D 0 mesons yielded by the fit were N tag (D 0 ) = 7281±104 and N untag (D 0 ) = 27787 ± 680 for selections with and without ∆M tag, respectively. The mass value obtained from the fit 3 describing the signal and a function of the form A · (∆M − m π ) B · e −C·∆M , describing the non-resonant background, was used to fit the data. Here m π is the pion mass and A, B and C are free parameters of the fit.…”

Measurement of beauty and charm production in deep inelastic scattering at HERA and measurement of the beauty-quark mass

“…For heavy-quark transverse momenta comparable to the quark mass, next-to-leading-order (NLO) QCD calculations based on the dynamical generation of the massive quarks [1][2][3][4] are expected to provide reliable predictions. Beauty and charm production in DIS has been measured using several methods by the H1 [5][6][7][8][9][10][11][12][13][14][15][16] and ZEUS [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] Inclusive jet cross sections in beauty and charm events are used in the analysis presented here to extract the heavy-quark contribution to the proton structure function F 2 with high precision, and to measure the b-quark mass. For this purpose, the long lifetimes of the weakly decaying b and c hadrons, which make the reconstruction of their decay vertices possible, as well as their large masses were exploited.…”

“…Beauty and charm production in DIS has been measured using several methods by the H1 [5][6][7][8][9][10][11][12][13][14][15][16] and ZEUS [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] collaborations. All but the two most recent measurements of…”