-
[show abstract]
[hide abstract]
ABSTRACT: A pair of gold nanowires, incorporated into a photonic crystal fiber, acts as a plasmonic "molecule." Hybridized modes are excited at specific wavelengths by launching light into the glass core. The formation of bonding and antibonding solutions results in a modal splitting of more than 100 nm, even though the spatial separation between the wires is larger than 3 μm. The study provides insight into multiwire plasmonic devices with applications as polarizers or filters in near-field optics, nonlinear plasmonics, optical sensing, and telecommunications.
Optics Letters 07/2012; 37(14):2946-8. · 3.40 Impact Factor
-
The CDF Collaboration,
T. Aaltonen,
J. Adelman,
B. Álvarez González,
S. Amerio,
D. Amidei,
A. Anastassov,
J. Antos,
G. Apollinari,
A. Apresyan, [......],
Y. C. Yang,
K. Yorita,
T. Yoshida,
G. B. Yu,
I. Yu,
S. S. Yu,
J. C. Yun,
A. Zanetti,
X. Zhang,
S. Zucchelli
[show abstract]
[hide abstract]
ABSTRACT: We report the results of a study of multi-muon events produced at the Fermilab Tevatron collider and acquired with the CDFII
detector using a dedicated dimuon trigger. The production cross section and kinematics of events in which both muon candidates
are produced inside the beam pipe of radius 1.5 cm are successfully modeled by known processes which include heavy flavor
production. In contrast, we are presently unable to fully account for the number and properties of the remaining events, in
which at least one muon candidate is produced outside of the beam pipe, in terms of the same understanding of the CDFII detector,
trigger, and event reconstruction.
European Physical Journal C 04/2012; 68(1):109-118. · 3.63 Impact Factor
-
CDF Collaboration,
T. Aaltonen,
J. Adelman,
T. Akimoto,
B. Álvarez González,
S. Amerio,
D. Amidei,
A. Anastassov,
A. Annovi,
J. Antos, [......],
T. Yoshida,
G. B. Yu,
I. Yu,
S. S. Yu,
J. C. Yun,
L. Zanello,
A. Zanetti,
X. Zhang,
Y. Zheng,
S. Zucchelli
[show abstract]
[hide abstract]
ABSTRACT: We report a search for narrow resonances, produced in
p[`(p)]p\bar{p}
collisions at
Ös=1.96\sqrt{s}=1.96
TeV, that decay into muon pairs with invariant mass between 6.3 and 9.0GeV/c
2. The data, collected with the CDFII detector at the Fermilab Tevatron collider, correspond to an integrated luminosity of
630pb−1. We use the dimuon invariant mass distribution to set 90% upper credible limits of about 1% to the ratio of the production
cross section times muonic branching fraction of possible narrow resonances to that of the ϒ(1S) meson.
European Physical Journal C 04/2012; 62(2):319-326. · 3.63 Impact Factor
-
T. Aaltonen,
J. Adelman,
B. Álvarez González,
S. Amerio,
D. Amidei,
A. Anastassov,
A. Annovi,
J. Antos,
G. Apollinari,
J. Appel, [......],
T. Yoshida,
G. B. Yu,
I. Yu,
S. S. Yu,
J. C. Yun,
A. Zanetti,
Y. Zeng,
X. Zhang,
Y. Zheng,
S. Zucchelli
[show abstract]
[hide abstract]
ABSTRACT: The collection of a large number of B-hadron decays to hadronic final states at the CDF II Detector is possible due to the presence of a trigger that selects events based on track impact parameters. However, the nature of the selection requirements of the trigger introduces a large bias in the observed proper-decay-time distribution. A lifetime measurement must correct for this bias, and the conventional approach has been to use a Monte Carlo simulation. The leading sources of systematic uncertainty in the conventional approach are due to differences between the data and the Monte Carlo simulation. In this paper, we present an analytic method for bias correction without using simulation, thereby removing any uncertainty due to the differences between data and simulation. This method is presented in the form of a measurement of the lifetime of the B- using the mode B-→D0π-. The B- lifetime is measured as τB-=1.663±0.023±0.015 ps, where the first uncertainty is statistical and the second systematic. This new method results in a smaller systematic uncertainty in comparison to methods that use simulation to correct for the trigger bias.
Phys. Rev. D. 02/2011; 83(3).
-
T. Aaltonen,
J. Adelman,
B. Álvarez González,
S. Amerio,
D. Amidei,
A. Anastassov,
A. Annovi,
J. Antos,
G. Apollinari,
J. Appel, [......],
T. Yoshida,
G. B. Yu,
I. Yu,
S. S. Yu,
J. C. Yun,
A. Zanetti,
Y. Zeng,
X. Zhang,
Y. Zheng,
S. Zucchelli
[show abstract]
[hide abstract]
ABSTRACT: We report the observation of electroweak single top quark production in 3.2 fb-1 of pp̅ collision data collected by the Collider Detector at Fermilab at √s=1.96 TeV. Candidate events in the W+jets topology with a leptonically decaying W boson are classified as signal-like by four parallel analyses based on likelihood functions, matrix elements, neural networks, and boosted decision trees. These results are combined using a super discriminant analysis based on genetically evolved neural networks in order to improve the sensitivity. This combined result is further combined with that of a search for a single top quark signal in an orthogonal sample of events with missing transverse energy plus jets and no charged lepton. We observe a signal consistent with the standard model prediction but inconsistent with the background-only model by 5.0 standard deviations, with a median expected sensitivity in excess of 5.9 standard deviations. We measure a production cross section of 2.3-0.5+0.6(stat+sys) pb, extract the value of the Cabibbo-Kobayashi-Maskawa matrix element |Vtb|=0.91-0.11+0.11(stat+sys)±0.07 (theory), and set a lower limit |Vtb|>0.71 at the 95% C.L., assuming mt=175 GeV/c2.
Phys. Rev. D. 12/2010; 82(11).
-
T Aaltonen,
J Adelman,
B Alvarez González,
S Amerio,
D Amidei,
A Anastassov,
A Annovi,
J Antos,
G Apollinari,
J Appel, [......],
T Yoshida,
G B Yu,
I Yu,
S S Yu,
J C Yun,
A Zanetti,
Y Zeng,
X Zhang,
Y Zheng,
S Zucchelli
[show abstract]
[hide abstract]
ABSTRACT: We present a search for supersymmetric neutrino ν production using the Tevatron pp collision data collected with the CDF II detector and corresponding to an integrated luminosity of 1 fb-1. We focus on the scenarios predicted by the R-parity violating (RPV) supersymmetric models in which sneutrinos decay to two charged leptons of different flavor. With the data consistent with the standard model expectations, we set upper limits on σ(pp→ν)×BR(ν→eμ,μτ,eτ) and use these results to constrain the RPV couplings as a function of the sneutrino mass.
Physical Review Letters 11/2010; 105(19):191801. · 7.37 Impact Factor
-
T. Aaltonen,
J. Adelman,
B. Álvarez González,
S. Amerio,
D. Amidei,
A. Anastassov,
A. Annovi,
J. Antos,
G. Apollinari,
A. Apresyan, [......],
T. Yoshida,
G. B. Yu,
I. Yu,
S. S. Yu,
J. C. Yun,
A. Zanetti,
Y. Zeng,
X. Zhang,
Y. Zheng,
S. Zucchelli
[show abstract]
[hide abstract]
ABSTRACT: We present results of a search for anomalous production of two photons together with an electron, muon, τ lepton, missing transverse energy, or jets using pp̅ collision data from 1.1–2.0 fb-1 of integrated luminosity collected by the Collider Detector at Fermilab (CDF). The event yields and kinematic distributions are examined for signs of new physics without favoring a specific model of new physics. The results are consistent with the standard model expectations. The search employs several new analysis techniques that significantly reduce instrumental backgrounds in channels with an electron and missing transverse energy.
Phys. Rev. D. 09/2010; 82(5).
-
T Aaltonen,
J Adelman,
B Alvarez González,
S Amerio,
D Amidei,
A Anastassov,
A Annovi,
J Antos,
G Apollinari,
J Appel, [......],
T Yoshida,
G B Yu,
I Yu,
S S Yu,
J C Yun,
A Zanetti,
Y Zeng,
X Zhang,
Y Zheng,
S Zucchelli
[show abstract]
[hide abstract]
ABSTRACT: We present a measurement of the electric charge of the top quark using pp collisions corresponding to an integrated luminosity of 2.7 fb(-1) at the CDF II detector. We reconstruct tt events in the lepton + jets final state. We use soft lepton taggers to determine the flavor of the b jets, which we use to reconstruct the top quark's electric charge and exclude an exotic top quark with -4/3 charge at 95% confidence level. This is the strongest exclusion of the exotic charge scenario and the first to use soft leptons for this purpose.
Physical Review Letters 09/2010; 105(10):101801. · 7.37 Impact Factor
-
T Aaltonen,
J Adelman,
B Alvarez González,
S Amerio,
D Amidei,
A Anastassov,
A Annovi,
J Antos,
G Apollinari,
A Apresyan, [......],
T Yoshida,
G B Yu,
I Yu,
S S Yu,
J C Yun,
A Zanetti,
Y Zeng,
X Zhang,
Y Zheng,
S Zucchelli
[show abstract]
[hide abstract]
ABSTRACT: We present results of a signature-based search for new physics using a dijet plus missing transverse energy (E(T)) data sample collected in 2 fb⁻¹ of pp collisions at √s=1.96 TeV with the CDF II detector at the Fermilab Tevatron. We observe no significant event excess with respect to the standard model prediction and extract a 95% C.L. upper limit on the cross section times acceptance for a potential contribution from a nonstandard model process. The search is made by using novel, data-driven techniques for estimating backgrounds that are applicable to first searches at the LHC.
Physical Review Letters 09/2010; 105(13):131801. · 7.37 Impact Factor
-
T Aaltonen,
J Adelman,
B Alvarez González,
S Amerio,
D Amidei,
A Anastassov,
A Annovi,
J Antos,
G Apollinari,
A Apresyan, [......],
T Yoshida,
G B Yu,
I Yu,
S S Yu,
J C Yun,
A Zanetti,
Y Zeng,
X Zhang,
Y Zheng,
S Zucchelli
[show abstract]
[hide abstract]
ABSTRACT: We report on a search for direct scalar bottom quark (sbottom) pair production in pp collisions at square root(s) = 1.96 TeV, in events with large missing transverse energy and two jets of hadrons in the final state, where at least one of the jets is required to be identified as originating from a b quark. The study uses a collider detector at Fermilab Run II data sample corresponding to 2.65 fb(-1) of integrated luminosity. The data are in agreement with the standard model. In an R-parity conserving minimal supersymmetric scenario, and assuming that the sbottom decays exclusively into a bottom quark and a neutralino, 95% confidence-level upper limits on the sbottom pair production cross section of 0.1 pb are obtained. For neutralino masses below 70 GeV/c2, sbottom masses up to 230 GeV/c2 are excluded at 95% confidence level.
Physical Review Letters 08/2010; 105(8):081802. · 7.37 Impact Factor
-
T. Aaltonen,
J. Adelman,
B. Álvarez González,
S. Amerio,
D. Amidei,
A. Anastassov,
A. Annovi,
J. Antos,
G. Apollinari,
A. Apresyan, [......],
T. Yoshida,
G. B. Yu,
I. Yu,
S. S. Yu,
J. C. Yun,
A. Zanetti,
Y. Zeng,
X. Zhang,
Y. Zheng,
S. Zucchelli
[show abstract]
[hide abstract]
ABSTRACT: We study the underlying event in proton-antiproton collisions by examining the behavior of charged particles produced in association with a large transverse momentum jet (∼2.2 fb-1) or with a Drell-Yan lepton pair (∼2.7 fb-1) in the Z-boson mass region [70<M(pair)<110 GeV/c2] as measured by CDF at 1.96 TeV center-of-mass energy. We use the direction of the lepton pair or the leading jet in each event to define regions of η-ϕ space that are sensitive to the modeling of the underlying event. The data are corrected to the particle level to remove detector effects and are then compared with several QCD Monte Carlo models.
Phys. Rev. D. 08/2010; 82(3).
-
T Aaltonen,
J Adelman,
B Alvarez González,
S Amerio,
D Amidei,
A Anastassov,
A Annovi,
J Antos,
G Apollinari,
J Appel, [......],
T Yoshida,
G B Yu,
I Yu,
S S Yu,
J C Yun,
A Zanetti,
Y Zeng,
X Zhang,
Y Zheng,
S Zucchelli
[show abstract]
[hide abstract]
ABSTRACT: We report measurements of the polarization of W bosons from top-quark decays using 2.7 fb{-1} of pp collisions collected by the CDF II detector. Assuming a top-quark mass of 175 GeV/c{2}, three measurements are performed. A simultaneous measurement of the fraction of longitudinal (f{0}) and right-handed (f{+}) W bosons yields the model-independent results f{0}=0.88±0.11(stat)±0.06(syst) and f{+}=-0.15±0.07(stat)±0.06(syst) with a correlation coefficient of -0.59. A measurement of f{0} [f{+}] constraining f{+} [f{0}] to its standard model value of 0.0 [0.7] yields f{0}=0.70±0.07(stat)±0.04(syst) [f{+}=-0.01±0.02(stat)±0.05(syst)]. All these results are consistent with standard model expectations. We achieve the single most precise measurements of f{0} for both the model-independent and model-dependent determinations.
Physical Review Letters 07/2010; 105(4):042002. · 7.37 Impact Factor
-
T Aaltonen,
J Adelman,
B Alvarez González,
S Amerio,
D Amidei,
A Anastassov,
A Annovi,
J Antos,
G Apollinari,
A Apresyan, [......],
T Yoshida,
G B Yu,
I Yu,
S S Yu,
J C Yun,
A Zanetti,
Y Zeng,
X Zhang,
Y Zheng,
S Zucchelli
[show abstract]
[hide abstract]
ABSTRACT: We report a measurement of the ratio of the tt to Z/γ{*} production cross sections in sqrt[s]=1.96 TeV pp collisions using data corresponding to an integrated luminosity of up to 4.6 fb{-1}, collected by the CDF II detector. The tt cross section ratio is measured using two complementary methods, a b-jet tagging measurement and a topological approach. By multiplying the ratios by the well-known theoretical Z/γ{*}→ll cross section predicted by the standard model, the extracted tt cross sections are effectively insensitive to the uncertainty on luminosity. A best linear unbiased estimate is used to combine both measurements with the result σ{tt}=7.70±0.52 pb, for a top-quark mass of 172.5 GeV/c{2}.
Physical Review Letters 07/2010; 105(1):012001. · 7.37 Impact Factor
-
T Aaltonen,
J Adelman,
T Akimoto,
B Alvarez González,
S Amerio,
D Amidei,
A Anastassov,
A Annovi,
J Antos,
G Apollinari, [......],
T Yoshida,
G B Yu,
I Yu,
S S Yu,
J C Yun,
L Zanello,
A Zanetti,
X Zhang,
Y Zheng,
S Zucchelli
[show abstract]
[hide abstract]
ABSTRACT: We present the results of a search for pair production of the supersymmetric partner of the top quark (the top squark t{1}) decaying to a b quark and a chargino χ{1}{±} with a subsequent χ{1}{±} decay into a neutralino χ{1}{0}, lepton ℓ, and neutrino ν. Using a data sample corresponding to 2.7 fb{-1} of integrated luminosity of pp collisions at sqrt[s]=1.96 TeV collected by the CDF II detector, we reconstruct the mass of top squark candidate events and fit the observed mass spectrum to a combination of standard model processes and t{1}t{1} signal. We find no evidence for t{1}t{1} production and set 95% C.L. limits on the masses of the top squark and the neutralino for several values of the chargino mass and the branching ratio B(χ{1}{±}→χ{1}{0}ℓ{±}ν).
Physical Review Letters 06/2010; 104(25):251801. · 7.37 Impact Factor
-
T Aaltonen,
J Adelman,
B Alvarez González,
S Amerio,
D Amidei,
A Anastassov,
A Annovi,
J Antos,
G Apollinari,
J Appel, [......],
T Yoshida,
G B Yu,
I Yu,
S S Yu,
J C Yun,
A Zanetti,
Y Zeng,
X Zhang,
Y Zheng,
S Zucchelli
[show abstract]
[hide abstract]
ABSTRACT: Using data from 2.9 fb(-1) of integrated luminosity collected with the CDF II detector at the Tevatron, we search for resonances decaying into a pair of on-shell gauge bosons, WW or WZ, where one W decays into an electron and a neutrino, and the other boson decays into two jets. We observed no statistically significant excess above the expected standard model background, and we set cross section limits at 95% confidence level on G* (Randall-Sundrum graviton), Z', and W' bosons. By comparing these limits to theoretical cross sections, mass exclusion regions for the three particles are derived. The mass exclusion regions for Z' and W' are further evaluated as a function of their gauge coupling strength.
Physical Review Letters 06/2010; 104(24):241801. · 7.37 Impact Factor
-
T Aaltonen,
J Adelman,
B Alvarez González,
S Amerio,
D Amidei,
A Anastassov,
A Annovi,
J Antos,
G Apollinari,
A Apresyan, [......],
T Yoshida,
G B Yu,
I Yu,
S S Yu,
J C Yun,
A Zanetti,
Y Zeng,
X Zhang,
Y Zheng,
S Zucchelli
[show abstract]
[hide abstract]
ABSTRACT: This Letter describes the current most precise measurement of the W boson pair production cross section and most sensitive test of anomalous WWγ and WWZ couplings in pp collisions at a center-of-mass energy of 1.96 TeV. The WW candidates are reconstructed from decays containing two charged leptons and two neutrinos. Using data collected by the CDF II detector from 3.6 fb(-1) of integrated luminosity, a total of 654 candidate events are observed with an expected background of 320±47 events. The measured cross section is σ(pp→W+ W- +X)=12.1±0.9(stat)-1.4+1.6(syst) pb, which is in good agreement with the standard model prediction. The same data sample is used to place constraints on anomalous WWγ and WWZ couplings.
Physical Review Letters 05/2010; 104(20):201801. · 7.37 Impact Factor
-
T. Aaltonen,
J. Adelman,
B. Álvarez González,
S. Amerio,
D. Amidei,
A. Anastassov,
A. Annovi,
J. Antos,
G. Apollinari,
J. Appel, [......],
T. Yoshida,
G. B. Yu,
I. Yu,
S. S. Yu,
J. C. Yun,
A. Zanetti,
Y. Zeng,
X. Zhang,
Y. Zheng,
S. Zucchelli
[show abstract]
[hide abstract]
ABSTRACT: We report a search for single top quark production with the CDF II detector using 2.1 fb-1 of integrated luminosity of pp̅ collisions at √s=1.96 TeV. The data selected consist of events characterized by large energy imbalance in the transverse plane and hadronic jets, and no identified electrons and muons, so the sample is enriched in W→τν decays. In order to suppress backgrounds, additional kinematic and topological requirements are imposed through a neural network, and at least one of the jets must be identified as a b quark jet. We measure an excess of signal-like events in agreement with the standard model prediction, but inconsistent with a model without single top quark production by 2.1 standard deviations (σ), with a median expected sensitivity of 1.4σ. Assuming a top quark mass of 175 GeV/c2 and ascribing the excess to single top quark production, the cross section is measured to be 4.9-2.2+2.5(stat+syst) pb, consistent with measurements performed in independent data sets and with the standard model prediction.
Phys. Rev. D. 04/2010; 81(7).
-
T Aaltonen,
J Adelman,
B Alvarez González,
S Amerio,
D Amidei,
A Anastassov,
A Annovi,
J Antos,
G Apollinari,
A Apresyan, [......],
T Yoshida,
G B Yu,
I Yu,
S S Yu,
J C Yun,
A Zanetti,
Y Zeng,
X Zhang,
Y Zheng,
S Zucchelli
[show abstract]
[hide abstract]
ABSTRACT: We report on a search for the standard model Higgs boson produced in association with a W or Z boson in pp collisions at square root(s)=1.96 TeV recorded by the CDF II experiment at the Tevatron in a data sample corresponding to an integrated luminosity of 2.1 fb(-1). We consider events which have no identified charged leptons, an imbalance in transverse momentum, and two or three jets where at least one jet is consistent with originating from the decay of a b hadron. We find good agreement between data and background predictions. We place 95% confidence level upper limits on the production cross section for several Higgs boson masses ranging from 110 GeV/c(2) to 150 GeV/c(2). For a mass of 115 GeV/c(2) the observed (expected) limit is 6.9 (5.6) times the standard model prediction.
Physical Review Letters 04/2010; 104(14):141801. · 7.37 Impact Factor
-
T Aaltonen,
J Adelman,
T Akimoto,
B Alvarez González,
S Amerio,
D Amidei,
A Anastassov,
A Annovi,
J Antos,
G Apollinari, [......],
T Yoshida,
G B Yu,
I Yu,
S S Yu,
J C Yun,
L Zanello,
A Zanetti,
X Zhang,
Y Zheng,
S Zucchelli
[show abstract]
[hide abstract]
ABSTRACT: The cross section for jets from b quarks produced with a W boson has been measured in pp collision data from 1.9 fb(-1) of integrated luminosity recorded by the CDF II detector at the Tevatron. The W+b-jets process poses a significant background in measurements of top quark production and prominent searches for the Higgs boson. We measure a b-jet cross section of 2.74+/-0.27(stat)+/-0.42(syst) pb in association with a single flavor of leptonic W boson decay over a limited kinematic phase space. This measured result cannot be accommodated in several available theoretical predictions.
Physical Review Letters 04/2010; 104(13):131801. · 7.37 Impact Factor
-
T. Aaltonen,
J. Adelman,
B. Álvarez González,
S. Amerio,
D. Amidei,
A. Anastassov,
A. Annovi,
J. Antos,
G. Apollinari,
J. Appel, [......],
G. B. Yu,
I. Yu,
S. S. Yu,
J. C. Yun,
A. Zanetti,
Y. Zeng,
X. Zhang,
Y. Zheng,
S. Zucchelli,
CDF Collaboration
[show abstract]
[hide abstract]
ABSTRACT: We report a search for single top quark production with the CDF II
detector using 2.1fb-1 of integrated luminosity of pp¯
collisions at s=1.96TeV. The data selected consist of events
characterized by large energy imbalance in the transverse plane and
hadronic jets, and no identified electrons and muons, so the sample is
enriched in W→τν decays. In order to suppress backgrounds,
additional kinematic and topological requirements are imposed through a
neural network, and at least one of the jets must be identified as a b
quark jet. We measure an excess of signal-like events in agreement with
the standard model prediction, but inconsistent with a model without
single top quark production by 2.1 standard deviations (σ), with a
median expected sensitivity of 1.4σ. Assuming a top quark mass of
175GeV/c2 and ascribing the excess to single top quark
production, the cross section is measured to be
4.9-2.2+2.5(stat+syst)pb, consistent with
measurements performed in independent data sets and with the standard
model prediction.
Physical review D: Particles and fields 03/2010; 81(7):72003.
