We present the report of the hadronic working group of the BOOST2010 workshop held at the University of Oxford in June 2010. The first part contains a review of the potential of hadronic decays of ...highly boosted particles as an aid for discovery at the LHC and a discussion of the status of tools developed to meet the challenge of reconstructing and isolating these topologies. In the second part, we present new results comparing the performance of jet grooming techniques and top tagging algorithms on a common set of benchmark channels. We also study the sensitivity of jet substructure observables to the uncertainties in Monte Carlo predictions.
Infrared-safe definition of jet flavour Banfi, A.; Salam, G.P.; Zanderighi, G.
European physical journal. C, Particles and fields,
07/2006, Letnik:
47, Številka:
1
Journal Article
Recenzirano
Odprti dostop
It is common, in both theoretical and experimental studies, to separately discuss quark and gluon jets. However, even at parton level, widely-used jet algorithms fail to provide an infrared-safe way ...of making this distinction. We examine the origin of the problem and propose a solution in terms of a new “flavour-kt” algorithm. As well as being of conceptual interest this can be a powerful tool when combining fixed-order calculations with multi-jet resummations and parton showers. It also has applications to studies of heavy-quark jets.
This remark is part of an ongoing project to simplify the structure of the multi-loop anomalous dimensions for parton distributions and fragmentation functions. It answers the call for a “structural ...explanation” of a “very suggestive” relation found by Moch, Vermaseren and Vogt in the context of the x→1 behaviour of three-loop DIS anomalous dimensions. It also highlights further structure that remains to be fully explained.
High-energy jets recoiling against missing transverse energy (MET) are powerful probes of dark matter at the LHC. Searches based on large MET signatures require a precise control of the
Z
(
ν
ν
¯
)
+
... jet background in the signal region. This can be achieved by taking accurate data in control regions dominated by
Z
(
ℓ
+
ℓ
-
)
+
jet,
W
(
ℓ
ν
)
+
jet and
γ
+
jet production, and extrapolating to the
Z
(
ν
ν
¯
)
+
jet background by means of precise theoretical predictions. In this context, recent advances in perturbative calculations open the door to significant sensitivity improvements in dark matter searches. In this spirit, we present a combination of state-of-the-art calculations for all relevant
V
+
jets processes, including throughout NNLO QCD corrections and NLO electroweak corrections supplemented by Sudakov logarithms at two loops. Predictions at parton level are provided together with detailed recommendations for their usage in experimental analyses based on the reweighting of Monte Carlo samples. Particular attention is devoted to the estimate of theoretical uncertainties in the framework of dark matter searches, where subtle aspects such as correlations across different
V
+
jet processes play a key role. The anticipated theoretical uncertainty in the
Z
(
ν
ν
¯
)
+
jet background is at the few percent level up to the TeV range.
Over the past decade, a large number of jet substructure observables have been proposed in the literature, and explored at the LHC experiments. Such observables attempt to utilize the internal ...structure of jets in order to distinguish those initiated by quarks, gluons, or by boosted heavy objects, such as top quarks and W bosons. This report, originating from and motivated by the BOOST2013 workshop, presents original particle-level studies that aim to improve our understanding of the relationships between jet substructure observables, their complementarity, and their dependence on the underlying jet properties, particularly the jet radius and jet transverse momentum. This is explored in the context of quark/gluon discrimination, boosted W boson tagging and boosted top quark tagging.
We discuss issues related to the resummation of non-global observables in QCD, those that are sensitive to radiation in only a part of phase space. Examples of such observables are certain ...single-hemisphere event shapes in
e
+
e
− and DIS. Compared to global observables (those sensitive to all emissions, e.g., the
e
+
e
− thrust) a new class of single-logarithmic terms arises. These have been neglected in recent calculations in the literature. For a whole set of single hemisphere
e
+
e
− and DIS event shapes, we analytically evaluate the first such term, at order
α
s
2, and give numerical results for the resummation of these terms in the large-
N
C
limit.
We discuss a practical formulation of backward evolution for the CCFM small-x evolution equation and show results from its implementation in the new Monte Carlo event-generator Cascade.
ABSTRACTThis study focuses on the Manimala River Basin (MMRB) situated in the Western Ghats region of Kerala, which has been significantly affected by landslides. The water quality in the MMRB is ...likely to be impacted by heavy rainfall and the resulting debris flows. A comprehensive analysis was conducted for 157 water samples collected from the MMRB, with an objective to evaluate the hydrogeological conditions and estimation of 23 physico-chemical parameters to determine the water quality. Pearson’s correlation matrix for geochemical data was performed to investigate the relationships among physical and chemical parameters, and various ions in the MMRB. The present study also aimed to identify the dominant geochemical facies present in the water samples and determine the geochemical processes responsible for modifying the hydrochemistry. The results revealed that elevated concentrations of Ca2+ and SO42- ions, which exert influence on the hydrochemistry of the region. Moreover, we utilized a fuzzy logic tool to categorize the water samples based on a water quality index, which indicated that approximately 92% of the MMRB samples are suitable for human consumption. This study offers valuable insights into the interplay of geochemical factors and water quality assessment, contributing to effective strategies for water resource management and conservation.
It is widely believed that at small x, the BFKL resummed gluon splitting function should grow as a power of 1/x. But in several recent calculations it has been found to decrease for moderately ...small-x before eventually rising. We show that this ‘dip’ structure is a rigorous feature of the Pgg splitting function for sufficiently small αs, the minimum occurring formally at log(1/x)∼1/αs. We calculate the properties of the dip, including corrections of relative order αs, and discuss how this expansion in powers of αs, which is poorly convergent, can be qualitatively matched to the fully resummed result of a recent calculation, for realistic values of αs. Finally, we note that the dip position, as a function of αs, provides a lower bound in x below which the NNLO fixed-order expansion of the splitting function breaks down and the resummation of small-x terms is mandatory.
This document describes a Fortran 95 package for carrying out DGLAP evolution and other common manipulations of parton distribution functions (PDFs). The PDFs are represented on a grid in
x-space so ...as to avoid limitations on the functional form of input distributions. Good speed and accuracy are obtained through the representation of splitting functions in terms of their convolution with a set of piecewise polynomial basis functions, and Runge–Kutta techniques are used for the evolution in
Q. Unpolarised evolution is provided to NNLO, including heavy-quark thresholds in the
MS
¯
scheme, and longitudinally polarised evolution to NLO. The code is structured so as to provide simple access to the objects representing splitting functions and PDFs, making it possible for a user to extend the facilities already provided. A streamlined interface is also available, facilitating use of the evolution part of the code from F77 and C/C++.
Program title: HOPPET
Catalogue identifier: AEBZ_v1_0
Program summary URL:
http://cpc.cs.qub.ac.uk/summaries/AEBZ_v1_0.html
Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland
Licensing provisions: GNU Public License
No. of lines in distributed program, including test data, etc.: 61 001
No. of bytes in distributed program, including test data, etc.: 270 312
Distribution format: tar.gz
Programming language: Fortran 95
Computer: All
Operating system: All
RAM: ≲10 MB
Classification: 11.5
Nature of problem: Solution of the DGLAP evolution equations up to NNLO (NLO) for unpolarised (longitudinally polarised) PDFs, and provision of tools to facilitate manipulation (convolutions, etc.) of PDFs with user-defined coefficient and splitting functions.
Solution method: Representation of PDFs on a grid in
x, adaptive integration of splitting functions to reduce them to a discretised form, obtaining fast convolutions that are equivalent to integration with an interpolated form of the PDFs; Runge–Kutta solution of the
Q evolution, and its caching so as to speed up repeated evolution with different initial conditions.
Restrictions: PDFs should be smooth on the scale of the discretisation in
x.
Running time: A few seconds for initialisation, then ∼10 ms for creating a tabulation with a relative accuracy of 10
−4 from a new initial condition (on a 3.4 GHz Pentium IV processor). Further details in Section 9.2.
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