Searcharxiv⌕ Search

SEARCH · Searcharxiv

Results for “hep-ex”

Search indexed arXiv papers on artificial intelligence, large language models, computer vision and robotics. Read source abstracts and follow links to arXiv.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4Linked to original sources
arXiv2007

Search for Single Top Quark Production Using Likelihood Discriminants at D0 in Run II

We present an improved search for single top quarks in two production modes, s-channel (tb) and t-channel (tqb). The search is performed in the electron+jets and muon+jets decay channels, with one or more b-tagged jets, on nearly 370 pb^{-1} of D0 Run II data collected between August 2002 and October 2004. Impact-parameter based b-quark tagging is used to select signal-like events. We use a likelihood discriminant method to separate signals from backgrounds. The resulting expected/observed 95% confidence level upper limits on the single top quark production cross sections are 3.3/5.0pb (s-channel) and 4.3/4.4pb (t-channel).

hep-ex↗
arXiv2007

W and Z Production and Asymmetries at the Tevatron

An overview of W and Z production in high energy hadron collisions is given. W and Z cross section and asymmetry measurements from CDF and DO are described, with particular emphasis on recent results. The current status of precision W mass and width measurements is reported. The fundamental physics parameters that can be extracted from these measurements are described, and the relevance of W and Z production studies for the LHC is pointed out.

hep-ex↗
arXiv2007

B-Tagging at CDF and DO, Lessons for LHC

The identification of jets resulting from the fragmentation and hadronization of b quarks is an important part of high-pT collider physics. The methods used by the CDF and DO collaborations to perform this identification are described, including the calibration of the efficiencies and fake rates. Some thoughts on the application of these methods in the LHC environment are also presented.

hep-ex↗
arXiv2007

New results from the B factories Belle and BaBar

The BELLE detector has already accumulated e^+ e^- collision data at the KEKB-collider corresponding to 600 fb^-1. BaBar has accumulated data of approximately 390 fb^-1 at PEP-II. Both are running on asymmetric energy e^+ e^- colliders at the Upsilon(4S) energy. The paper selects important results from both experiments with the emphasis on CP violation in B meson decays and its implications for the Unitarity Triangle.

hep-ex↗
arXiv2007

KLOE measurement of the charged kaon absolute semileptonic BR's

This paper is devoted to the measurement of the fully inclusive absolute branching ratios of the charged kaon semileptonic decays, $K^{\pm}\toπ^0e^\pmν(γ)$ and $K^\pm \to π^0μ^\pmν(γ)$. The measurements have been done using a tag technique, employing the two-body decays, $K^\pm \to μ^\pmν$ and $K^\pm \to π^\pmπ^0$, and using a sample of about 410 pb$^{-1}$ collected during the 2001 and 2002 data taking of the KLOE experiment at Daphne, the Frascati $ϕ$-factory. The results obtained are BR(K$^\pm_{e3}$) = $0.04965 (38)_{Stat} (37)_{Syst}$ and BR(K$^\pm_{\mu3}$) = $0.03233 (29)_{Stat} (26)_{Syst}$.

hep-ex↗
arXiv2007

Non-planar structure of analytical QCD predictions for the Gottfried sum rule

It is stressed that within large N_c-expansion {\bf analytical calculations} of the $(α_s/π)^2$ QCD contributions to the valence part of the Gottfried sum rule for F_2 structure function of charged leptons-nucleon deep-inelastic scattering reveals the existence of the $O(1/N_c^2)$ {\bf non-planar} corrections only and the disappearance of the {\bf planar} O(N_c^0) perturbative terms. The relation between Gottfried and Adler sum rule for neutino-nucleon DIS is established and the proposal that the differebce between corresponding QCD corrections to higher non-singlet moments in charged-lepton and neutrino DIS are {\bf suppressed by 1/N_c^2} is made. The possible consequence of the cancellation of {\bf perturbative planar} graphs in the considered perturbative series, namely the existence of light-quark flavour asymmetry $\bar{u}(x)<\bar{d}(x)$, is mentioned. The effect of the similar origin, i.e. the relation of {\bf ``light-by-light-type''-type structure} in DIS characteristics at the $α_s^3$-level to the generation of light quark-antiquark asymmetry, is also commented.

hep-ph↗
arXiv2007

Dalitz plot analysis of the D+ -> K- pi+ pi+ decay

We present a Dalitz plot analysis of the decay D+ -> K- pi+ pi+ based on 281 pb-1 of e+e- collision data produced at the psi(3770) by CESR and observed with the CLEO-c detector. We select 67086 candidate events with a small, ~1.1%, background for this analysis. When using a simple isobar model our results are consistent with the previous measurements done by E791. Since our sample is considerably larger we can explore alternative models. We find better agreement with data when we include an isospin-two pi+pi+ S-wave contribution. We apply a quasi model-independent partial wave analysis and measure the amplitude and phase of the K pi and pi+pi+ S waves in the range of invariant masses from the threshold to the maximum in this decay.

hep-ex↗
arXiv2007

Autonomous tools for Grid management, monitoring and optimization

We outline design and lines of development of autonomous tools for the computing Grid management, monitoring and optimization. The management is proposed to be based on the notion of utility. Grid optimization is considered to be application-oriented. A generic Grid simulator is proposed as an optimization tool for Grid structure and functionality.

cs.DC↗
arXiv2007

Search for Excited Leptons at HERA

Searches for excited electrons and neutrinos have been performed using the complete HERA I and II data samples collected by the H1 detector at $\sqrt{s}=320$ GeV corresponding to an integrated luminosity of up to 435 pb$^{-1}$. In absence of a signal, the limits on the ratio of the coupling to the compositeness scale derived extend the excluded region to higher masses than has been possible in previous searches.

hep-ex↗
arXiv2007

Branching ratio measurement of $K_S\to γγ$ decay using a pure $\ks$ beam in the KLOE detector

We have analyzed 1.62 fb$^{-1}$ of $e^{+}e^{-}$ collisions at a center of mass energy $\sim M_ϕ$ collected by the KLOE experiment at DA$Φ$NE. This sample corresponds to a production of $\sim$ 1.7 billion of $\ks$ $\kl$ pairs which allowed us to search for the rare $K_S\to γγ$ decay. $K_S$ are tagged by the $K_L$ interaction in the calorimeter and the signal is searched for by requiring two additional prompt photons. Strong kinematic requirements reduce the initial 0.5$\times 10^6$ events to 2300 candidates from which we extract a signal of 600 $\pm$ 35 events. By normalizing to the $\ks \to 2 π^0$ decays counted in the same sample, the measured value of BR($\ks \to γγ$) is (2.27 $\pm 0.13(stat.) ^{+0.03}_{-0.04} (syst.)) \times 10^{-6}$, in agreement with $O(P^4)$ Chiral Perturbation Theory predictions.

hep-ex↗
arXiv2007

Inclusive Jet Production in DIS at High Q^2 and Extraction of the Strong Coupling

Inclusive jet production is studied in neutral current deep-inelastic positron-proton scattering at large four momentum transfer squared Q^2>150 GeV^2 with the H1 detector at HERA. The measurements are found to be well described by calculations at next-to-leading order in perturbative QCD. The running of the strong coupling is demonstrated and the value of alpha_s(M_Z) is determined.

hep-ex↗
arXiv2007

KLOE extraction of $a_μ^{ππ}$ in the mass range [0.35,0.95] GeV^2

The KLOE Experiment at the $ϕ$ factory DA$Φ$NE, has measured the cross section $σ(e^+e^-\toπ^+π^-γ)$ using two different selection schemes: requiring the photon emission at small polar angle and detecting the photon at large polar angle in the calorimeter. Using a theoretical radiator function we extract the pion form factor and obtain the $ππ$ contribution to the anomalous magnetic moment of the muon. Results presented here come from the analysis of 240 pb^{-1} collected in 2002, with improved systematic uncertainty with respect to the published KLOE analysis. We also include an update of the previous analysis.

hep-ex↗
arXiv2007

Search for phi to K0 K0bar gamma decay with KLOE

The KLOE collaboration has searched for the phi to K0 K0bar gamma decay using a sample of 1.4 fb-1 of e+e- collisions at W ~ M(phi) collected with the KLOE experiment at the Frascati e+e- collider DAFNE. No previous search exists for this decay, while many theory models predict a BR of 10-8 for this channel. We set a preliminary value of the U.L. on this BR to 1.8x10-8 at 90% C.L.. This limit rules out most of the existing theory predictions.

hep-ex↗
arXiv2007

Study of the radiative decay phi to a0(980) gamma with the KLOE detector

A sample of 1.25x10^9 phi decays, collected with the KLOE detector at the Frascati phi-factory DAFNE at center of mass energy ~ Mphi, has been used to study the radiative decay phi to eta pi0 gamma. This decay is dominated by phi to a0(980) gamma. Two decay chains, corresponding to eta to gamma gamma and eta to pi+ pi- pi0, have been selected. We found respectively: Br(phi to eta pi0 gamma)=(6.92 +/- 0.10 (stat.) +/- 0.20 (syst.))x10^(-5) and (7.19 +/- 0.17 (stat.) +/- 0.24 (syst.))x 10 ^(-5). The eta pi0 invariant mass distributions have been fitted to obtain the relevant a0(980) parameters.

hep-ex↗
arXiv2007

Measurements of the form-factors slopes of KL -> pi mu nu decay with the KLOE Detector

We present a measurement of the K-$π$ form-factor parameters for the decay \klpmn. We use 328 pb^{-1} of data collected in 2001 and 2002, corresponding to $\sim $ 1.8 million \semil events. Measurements of semileptonic form factors provide information about the dynamics of the strong interaction and are necessary for evaluation of the phase-space integral $I^μ_K$ needed to measure the CKM matrix element $|V_{us}|$ for \klpmn decays and to test lepton universality in kaon decays. Using a new parameterization for the vector and scalar form factors we find $λ_+$=\pt(25.6\pm 0.4_{\rm{stat.}}\pm 0.3_{\rm{syst.}}),-3, and $λ_0$=\pt(14.3\pm 1.7_{\rm{stat.}}\pm 1.1_{\rm{stat.}}),-3,. In the more usual quadratic expansion of the form factor the above result is corresponds to $λ'_+=λ_+$, $λ''_+=2λ^2_+$, $λ'_0=λ_0$ and $λ''_0=(λ^2_0+0.000416)/2$. Our results, together with recent lattice calculations of $f_π$, $f_K$ and $f(0)$, satisfy the Callan-Trieman relation.

hep-ex↗