85 research outputs found
Recombination Algorithms and Jet Substructure: Pruning as a Tool for Heavy Particle Searches
We discuss jet substructure in recombination algorithms for QCD jets and
single jets from heavy particle decays. We demonstrate that the jet algorithm
can introduce significant systematic effects into the substructure. By
characterizing these systematic effects and the substructure from QCD,
splash-in, and heavy particle decays, we identify a technique, pruning, to
better identify heavy particle decays into single jets and distinguish them
from QCD jets. Pruning removes protojets typical of soft, wide angle radiation,
improves the mass resolution of jets reconstructing a heavy particle decay, and
decreases the QCD background. We show that pruning provides significant
improvements over unpruned jets in identifying top quarks and W bosons and
separating them from a QCD background, and may be useful in a search for heavy
particles.Comment: 33 pages, 42 figure
XCone: N-jettiness as an exclusive cone jet algorithm
We introduce a new jet algorithm called XCone, for eXclusive Cone, which is based on minimizing the event shape N -jettiness. Because N -jettiness partitions every event into N jet regions and a beam region, XCone is an exclusive jet algorithm that always returns a fixed number of jets. We use a new “conical geometric” measure for which well-separated jets are bounded by circles of radius R in the rapidity-azimuth plane, while overlapping jet regions automatically form nearest-neighbor “clover jets”. This avoids the split/merge criteria needed in inclusive cone algorithms. A key feature of XCone is that it smoothly transitions between the resolved regime where the N signal jets of interest are well separated and the boosted regime where they overlap. The returned value of N -jettiness also provides a quality criterion of how N -jet-like the event looks. We also discuss the N -jettiness factorization theorems that occur for various jet measures, which can be used to compute the associated exclusive N -jet cross sections. In a companion paper [1], the physics potential of XCone is demonstrated using the examples of dijet resonances, Higgs decays to bottom quarks, and all-hadronic top pairs.United States. Department of Energy (Offices of Nuclear and Particle Physics Contracts DE-SC00012567 and DE-SC0011090)Simons Foundation (Investigator grant 327942)United States. Department of Energy (Early Career research program DE-SC0006389)Alfred P. Sloan Foundation (Sloan Research Fellowship)Massachusetts Institute of Technology. Undergraduate Research Opportunities Program (Paul E. Gray Endowed Fund
Consistent Factorization of Jet Observables in Exclusive Multijet Cross-Sections
We demonstrate the consistency at the next-to-leading-logarithmic (NLL) level
of a factorization theorem based on Soft-Collinear Effective Theory (SCET) for
jet shapes in e+e- collisions. We consider measuring jet observables in
exclusive multijet final states defined with cone and k_T-type jet algorithms.
Consistency of the factorization theorem requires that the renormalization
group evolution of hard, jet, and soft functions is such that the physical
cross-section is independent of the factorization scale mu. The anomalous
dimensions of the various factorized pieces, however, depend on the color
representation of jets, choice of jet observable, the number of jets whose
shapes are measured, and the jet algorithm, making it highly nontrivial to
satisfy the consistency condition. We demonstrate the intricate cancellations
between anomalous dimensions that occur at the NLL level, so that, up to power
corrections that we identify, our factorization of the jet shape distributions
is consistent for any number of quark and gluon jets, for any number of jets
whose shapes are measured or unmeasured, for any angular size R of the jets,
and for any of the algorithms we consider. Corrections to these results are
suppressed by the SCET expansion parameter lambda (the ratio of soft to
collinear or collinear to hard scales) and in the jet separation measure 1/t^2
= tan^2(R/2)/tan^2(psi/2), where psi is the angular separation between jets.
Our results can be used to calculate a wide variety of jet observables in
multijet final states to NLL accuracy.Comment: 8 pages, 1 figure, uses elsarticle.cls; v2: minor edits, added
reference
Jet Substructure at the Tevatron and LHC: New results, new tools, new benchmarks
In this report we review recent theoretical progress and the latest
experimental results in jet substructure from the Tevatron and the LHC. We
review the status of and outlook for calculation and simulation tools for
studying jet substructure. Following up on the report of the Boost 2010
workshop, we present a new set of benchmark comparisons of substructure
techniques, focusing on the set of variables and grooming methods that are
collectively known as "top taggers". To facilitate further exploration, we have
attempted to collect, harmonise, and publish software implementations of these
techniques.Comment: 53 pages, 17 figures. L. Asquith, S. Rappoccio, C. K. Vermilion,
editors; v2: minor edits from journal revision
Jet Shapes and Jet Algorithms in SCET
Jet shapes are weighted sums over the four-momenta of the constituents of a
jet and reveal details of its internal structure, potentially allowing
discrimination of its partonic origin. In this work we make predictions for
quark and gluon jet shape distributions in N-jet final states in e+e-
collisions, defined with a cone or recombination algorithm, where we measure
some jet shape observable on a subset of these jets. Using the framework of
Soft-Collinear Effective Theory, we prove a factorization theorem for jet shape
distributions and demonstrate the consistent renormalization-group running of
the functions in the factorization theorem for any number of measured and
unmeasured jets, any number of quark and gluon jets, and any angular size R of
the jets, as long as R is much smaller than the angular separation between
jets. We calculate the jet and soft functions for angularity jet shapes \tau_a
to one-loop order (O(alpha_s)) and resum a subset of the large logarithms of
\tau_a needed for next-to-leading logarithmic (NLL) accuracy for both cone and
kT-type jets. We compare our predictions for the resummed \tau_a distribution
of a quark or a gluon jet produced in a 3-jet final state in e+e- annihilation
to the output of a Monte Carlo event generator and find that the dependence on
a and R is very similar.Comment: 62 pages plus 21 pages of Appendices, 13 figures, uses JHEP3.cls. v2:
corrections to finite parts of NLO jet functions, minor changes to plots,
clarified discussion of power corrections. v3: Journal version. Introductory
sections significantly reorganized for clarity, classification of logarithmic
accuracy clarified, results for non-Mercedes-Benz configurations adde
Cytochrome P450 CYP1B1 activity in renal cell carcinoma
Renal cell carcinoma (RCC) is the most common malignancy of the kidney and has a poor prognosis due to its late presentation and resistance to current anticancer drugs. One mechanism of drug resistance, which is potentially amenable to therapeutic intervention, is based on studies in our laboratory. CYP1B1 is a cytochrome P450 enzyme overexpressed in a variety of malignant tumours. Our studies are now elucidating a functional role for CYP1B1 in drug resistance. Cytochrome P450 reductase (P450R) is required for optimal metabolic activity of CYP1B1. Both CYP1B1 and P450R can catalyse the biotransformation of anticancer drugs at the site of the tumour. In this investigation, we determined the expression of CYP1B1 and P450R in samples of normal kidney and RCC (11 paired normal and tumour and a further 15 tumour samples). The O-deethylation of ethoxyresorufin to resorufin was used to measure CYP1B1 activity in RCC. Cytochrome P450 reductase activity was determined by following the reduction of cytochrome c at 550 nm. The key finding of this study was the presence of active CYP1B1 in 70% of RCC. Coincubation with the CYP1B1 inhibitor alpha-naphthoflavone (10nM) inhibited this activity. No corresponding CYP1B1 activity was detected in any of the normal tissue examined (n = 11). Measurable levels of active P450R were determined in all normal (n = 11) and tumour samples (n = 26). The presence of detectable CYP1B1, which is capable of metabolising anticancer drugs in tumour cells, highlights a novel target for therapeutic intervention
The TESS Grand Unified Hot Jupiter Survey. II. Twenty New Giant Planets
NASA's Transiting Exoplanet Survey Satellite (TESS) mission promises to
improve our understanding of hot Jupiters by providing an all-sky,
magnitude-limited sample of transiting hot Jupiters suitable for population
studies. Assembling such a sample requires confirming hundreds of planet
candidates with additional follow-up observations. Here, we present twenty hot
Jupiters that were detected using TESS data and confirmed to be planets through
photometric, spectroscopic, and imaging observations coordinated by the TESS
Follow-up Observing Program (TFOP). These twenty planets have orbital periods
shorter than 7 days and orbit relatively bright FGK stars ().
Most of the planets are comparable in mass to Jupiter, although there are four
planets with masses less than that of Saturn. TOI-3976 b, the longest period
planet in our sample ( days), may be on a moderately eccentric orbit
(), while observations of the other targets are consistent
with them being on circular orbits. We measured the projected stellar obliquity
of TOI-1937A b, a hot Jupiter on a 22.4 hour orbit with the Rossiter-McLaughlin
effect, finding the planet's orbit to be well-aligned with the stellar spin
axis (). We also investigated the possibility that
TOI-1937 is a member of the NGC 2516 open cluster, but ultimately found the
evidence for cluster membership to be ambiguous. These objects are part of a
larger effort to build a complete sample of hot Jupiters to be used for future
demographic and detailed characterization work.Comment: 67 pages, 11 tables, 13 figures, 2 figure sets. Resubmitted to ApJS
after revision
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