6,440 research outputs found
Addressing the Multi-Channel Inverse Problem at High Energy Colliders: A Model Independent Approach to the Search for New Physics with Trileptons
We describe a method for interpreting trilepton searches at high energy
colliders in a model-independent fashion and apply it to the recent searches at
the Tevatron. The key step is to recognize that the trilepton signature is
comprised of four experimentally very different channels defined by the number
of tau-leptons in the trilepton state. Contributions from these multiple
channels to the overall experimental sensitivity (cross section times branching
ratio) are model-independent and can be parametrized in terms of relevant new
particle masses. Given the trileptonic branching ratios of a specific model,
these experimentally obtained multichannel sensitivities can be combined to
obtain a cross section measurement that can be used to confront the model with
data. Our model-independent results are more widely applicable than the current
Tevatron trilepton results which are stated exclusively in terms of mSUGRA
parameters of supersymmetry. The technique presented here can be expanded
beyond trilepton searches to the more general "inverse problem" of
experimentally discriminating between competing models that seek to explain new
physics discovered in multiple channels.Comment: 17 pages, 7 figures Changed content cosmetic changes for submission
to JHE
VLASS tidal disruption events with optical flares II: discovery of two TDEs with intermediate width Balmer emission lines and connections to the ambiguous extreme coronal line emitters
The multiwavelength properties of radio-emitting tidal disruption events
(TDEs) are poorly understood. In a previous paper, we presented the first
sample of radio-selected, optically-detected TDEs, which included two events
(VT J1008 and VT J2012) associated with late-time ( years post-optical
flare) intermediate with emission lines that are largely unprecedented from
TDEs. In this paper, we investigate these two events in detail. The
multiwavelength properties of these events are otherwise consistent with
optically-selected TDEs. They are hosted by green valley, E+A/Balmer dominated
galaxies with low star formation rates and black holes masses . The optical flare shapes are fully consistent
with those of optically-selected TDEs, although they are slightly faint and
cool at peak. The radio emission from both events is consistent with
wide-angle, non-relativistic outflows with erg
s. Balmer and Helium emission lines are detected from both events with
full-width-half-maxima km s and asymmetric line profiles. VT
J1008 additionally shows coronal line emission with a similar width. The lines
from VT J2012 are redshifted by km s relative to the host
galaxy. We show that these events share many characteristics in common with the
ambiguous class of extreme coronal line emitters. We argue that the lines are
likely associated with a radiative shock or dense, photoionized clumps of
outflowing gas in the circumnuclear medium.Comment: 18 pages, 6 figures, submitted to Ap
Strong rescattering in K-> 3pi decays and low-energy meson dynamics
We present a consistent analysis of final state interactions in
decays in the framework of Chiral Perturbation Theory.
The result is that the kinematical dependence of the rescattering phases cannot
be neglected. The possibility of extracting the phase shifts from future
interference experiments is also analyzed.Comment: 14 pages in RevTex, 3 figures in postscrip
Searching for with Multi-Leptons
The results of a multi-lepton search conducted by the CMS collaboration with
5 fb of data collected from 7 TeV collisions are used to place the
first bound on the rare flavor-changing decay of the top quark to a Higgs boson
and charm quark. Combining results from a number of exclusive three- and
four-lepton search channels yields an estimated upper limit of for a Higgs boson mass of 125 GeV. The sensitivity of future
dedicated searches for could be improved by adding exclusive same
sign di-lepton channels, as well as by sub-dividing channels based on -quark
tagging and partial kinematic top quark and Higgs boson tagging. This bound may
be interpreted more widely within a range of new physics processes that yield
final states with a -boson in association with a Higgs boson. For such
processes with kinematics that are similar to top--anti-top production and
decay, the estimated limit on cross section times branching ratio corresponds
to roughly pb.Comment: 11 pages, 1 table; v2 typo correcte
Search for Light Gluinos via the Spontaneous Appearance of pi+pi- Pairs with an 800 GeV/c Proton Beam at Fermilab
We searched for the appearance of pi+pi- pairs with invariant mass greater
than 648 MeV in a neutral beam. Such an observation could signify the decay of
a long-lived light neutral particle. We find no evidence for this decay. Our
null result severely constrains the existence of an R0 hadron, which is the
lightest bound state of a gluon and a light gluino, and thereby also the
possibility of a light gluino. Depending on the photino mass, we exclude the R0
in the mass and lifetime ranges of 1.2 -- 4.6 GeV and 2E-10 -- 7E-4 seconds,
respectively. (To Appear in Phys. Rev. Lett.)Comment: Documentstyle aps,epsfig,prl (revtex), 6 pages, 7 figure
First Observation of the decay KL -> pi0 e e gamma
We report on the first observation of the decay KL -> pi0 ee gamma by the
KTeV E799 experiment at Fermilab. Based upon a sample of 48 events with an
estimated background of 3.6 +/- 1.1 events, we measure the KL -> pi0 ee gamma
branching ratio to be (2.34 +/- 0.35 +/- 0.13)x10^{-8}. Our data agree with
recent O(p^6) calculations in chiral perturbation theory that include
contributions from vector meson exchange through the parameter a_V. A fit was
made to the KL -> pi0 ee gamma data for a_V with the result -0.67 +/- 0.21 +/-
0.12, which is consistent with previous results from KTeV.Comment: Submitted to Physical Review Letters, 5 pages, 5 figure
Observation of CP Violation in K(L)->pi+pi-e+e- Decays
We report the first observation of a manifestly CP violating effect in the
K(L)->pi+pi-e+e- decay mode. A large asymmetry was observed in the distribution
of these decays in the CP-odd and T-odd angle phi between the decay planes of
the e+e- and pi+pi- pairs in the K(L) center of mass system. After acceptance
corrections, the overall asymmetry is found to be 13.6+-2.5 (stat) +-1.2
(syst)%. This is the largest CP-violating effect yet observed integrating over
the entire phase space of a mode and the first such effect observed in an
angular variable.Comment: 4 pages 4 figures submitted to pr
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