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M. Takeuchi

Publications and source records attributed to M. Takeuchi.

9 recordsLinked to original sources
arXiv2013

Boosted objects and jet substructure at the LHC

This report of the BOOST2012 workshop presents the results of four working groups that studied key aspects of jet substructure. We discuss the potential of the description of jet substructure in first-principle QCD calculations and study the accuracy of state-of-the-art Monte Carlo tools. Experimental limitations of the ability to resolve substructure are evaluated, with a focus on the impact of additional proton proton collisions on jet substructure performance in future LHC operating scenarios. A final section summarizes the lessons learnt during the deployment of substructure analyses in searches for new physics in the production of boosted top quarks.

hep-ex↗
arXiv2011

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.

hep-ph↗
arXiv2010

Boosted objects: a probe of beyond the Standard Model physics

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.

hep-ph↗
arXiv2008

New Physics at the LHC: A Les Houches Report. Physics at Tev Colliders 2007 -- New Physics Working Group

We present a collection of signatures for physics beyond the standard model that need to be explored at the LHC. The signatures are organized according to the experimental objects that appear in the final state, and in particular the number of high pT leptons. Our report, which includes brief experimental and theoretical reviews as well as original results, summarizes the activities of the "New Physics'' working group for the "Physics at TeV Colliders" workshop (Les Houches, France, 11-29 June, 2007).

hep-ph↗
arXiv2005

Paramagnetic Faraday rotation with spin-polarized ytterbium atoms

We report observation of the paramagnetic Faraday rotation of spin-polarized ytterbium (Yb) atoms. As the atomic samples, we used an atomic beam, released atoms from a magneto-optical trap (MOT), and trapped atoms in a far-off-resonant trap (FORT). Since Yb is diamagnetic and includes a spin-1/2 isotope, it is an ideal sample for the spin physics, such as quantum non-demolition measurement of spin (spin QND), for example. From the results of the rotation angle, we confirmed that the atoms were almost perfectly polarized.

quant-ph↗
arXiv2005

Fast polarimetry system for the application to spin quantum non-demolition measurement

We report the development of a fast pulse polarimeter for the application to quantum non-demolition measurement of atomic spin (Spin QND). The developed system was tunable to the atomic resonance of ytterbium atom and has narrow laser linewidth suitable for spin QND. Using the developed polarimeter, we successfully demonstrated the measurement of the vacuum noise, with 10^6 to 10^7 photon number per pulse.

quant-ph↗
arXiv2004

Spin Squeezing via One-Axis Twisting with Coherent Light

We propose a new method of spin squeezing of atomic spin, based on the interactions between atoms and off-resonant light which are known as paramagnetic Faraday rotation and fictitious magnetic field of light. Since the projection process, squeezed light, or special interactions among the atoms are not required in this method, it can be widely applied to many systems. The attainable range of the squeezing parameter is S^{-2/5}, where S is the total spin, which is limited by additional fluctuations imposed by coherent light and the spherical nature of the spin distribution.

quant-ph↗
arXiv1996

X-Ray Fluctuations from Locally Unstable Advection-Dominated Disks

The response of advection-dominated accretion disks to local disturbances is examined by one-dimensional numerical simulations. It is generally believed that advection-dominated disks are thermally stable. We, however, find that any disurbance added onto accretion flow at large radii does not decay so rapidly that it can move inward with roughly the free-fall velocity. Although disturbances continue to be present, the global disk structure will not be modified largely. This can account for persistent hard X-ray emission with substantial variations observed in active galactic nuclei and stellar black hole candidates during the hard state. Moreover, when the disturbance reaches the innermost parts, an acoustic wave emerges, propagating outward as a shock wave. The resultant light variation is roughly (time) symmetric and is quite reminiscent of the observed X-ray shots of Cygnus X-1.

astro-ph↗