130 research outputs found
Initial-state splitting kernels in cold nuclear matter
We derive medium-induced splitting kernels for energetic partons that undergo
interactions in dense QCD matter before a hard-scattering event at large
momentum transfer . Working in the framework of the effective theory , we compute the splitting kernels beyond the soft gluon
approximation. We present numerical studies that compare our new results with
previous findings. We expect the full medium-induced splitting kernels to be
most relevant for the extension of initial-state cold nuclear matter energy
loss phenomenology in both p+A and A+A collisions.Comment: 8 pages, 4 figure
QCD resummation for semi-inclusive hadron production processes
We investigate the resummation of large logarithmic perturbative corrections
to hadron production in electron-positron annihilation and semi-inclusive
deep-inelastic scattering. We find modest, but significant, enhancements of
hadron multiplicities in the kinematic regimes accessible in present
high-precision experiments. Our results are therefore relevant for the
determination of hadron fragmentation functions from data for these processes.Comment: 14 pages, 11 figure
Effective field theory approach to open heavy flavor production in heavy-ion collisions
We develop a version of Soft Collinear Effective Theory (SCET) which includes
finite quark masses, as well as Glauber gluons that describe the interaction of
collinear partons with QCD matter. In the framework of this new effective field
theory, labeled SCET, we derive the massive splitting
functions in the vacuum and the QCD medium for the processes , and . The numerical effects due to finite quark masses are
sizable and our results are consistent with the traditional approach to parton
energy loss in the soft gluon emission limit. In addition, we present a new
framework for including the medium-induced full splitting functions consistent
with next-to-leading order calculations in QCD for inclusive hadron production.
Finally, we show numerical results for the suppression of - and -mesons
in heavy ion collisions at TeV and 2.76 TeV and
compare to available data from the LHC.Comment: 43 pages, 14 figure
Threshold and jet radius joint resummation for single-inclusive jet production
We present the first threshold and jet radius jointly resummed cross section
for single-inclusive hadronic jet production. We work at next-to-leading
logarithmic accuracy and our framework allows for a systematic extension beyond
the currently achieved precision. Longstanding numerical issues are overcome by
performing the resummation directly in momentum space within Soft Collinear
Effective Theory. We present the first numerical results for the LHC and
observe an improved description of the available data. Our results are of
immediate relevance for LHC precision phenomenology including the extraction of
parton distribution functions and the QCD strong coupling constant.Comment: 5 pages, 3 figures, minor text changes, PDF uncertainties included
and more references added. Replaced to match the published versio
The semi-inclusive jet function in SCET and small radius resummation for inclusive jet production
We introduce a new kind of jet function: the semi-inclusive jet function
, which describes how a parton is transformed into a
jet with a jet radius and energy fraction , with
and being the large light-cone momentum component of the
jet and the corresponding parton that initiates the jet, respectively.
Within the framework of Soft Collinear Effective Theory (SCET) we calculate
both and to the next-to-leading
order (NLO) for cone and anti-k algorithms. We demonstrate that the
renormalization group (RG) equations for follow exactly
the usual DGLAP evolution, which can be used to perform the resummation
for {\it inclusive} jet cross sections with a small jet radius . We clarify
the difference between our RG equations for and those
for the so-called unmeasured jet functions , widely used in
SCET for {\it exclusive} jet production. Finally, we present applications of
the new semi-inclusive jet functions to inclusive jet production in
and collisions. We demonstrate that single inclusive jet production in
these collisions shares the same short-distance hard functions as single
inclusive hadron production, with only the fragmentation functions replaced by . This can facilitate more efficient
higher-order analytical computations of jet cross sections. We further match
our resummation at both LL and NLL to fixed NLO results and
present the phenomenological implications for single inclusive jet production
at the LHC.Comment: 35 pages, 11 figures, published version at JHE
The Jet Shape at NLL
The jet shape is the fraction of the jet energy within a cone centered on
the jet axis. We calculate the jet shape distribution at next-to-leading
logarithmic accuracy plus next-to-leading order (NLL), accounting for
logarithms of both the jet radius and the ratio . This is the first
phenomenological study that takes the recoil of the jet axis due to soft
radiation into account, which is needed to reach this accuracy, but complicates
the calculation of collinear radiation and requires the treatment of rapidity
logarithms and non-global logarithms. We present numerical results, finding
good agreement with ATLAS and CMS measurements of the jet shape in an inclusive
jet sample, , for different kinematic bins. The effect of
the underlying event and hadronization are included using a simple
one-parameter model, since they are not part of our perturbative calculation.Comment: 36 pages, 14 figures, v2: extended discussion of non-global
logarithms, journal versio
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