Showing papers by "D. M. Strom published in 2009"

Observation of single top-quark production

Abstract: We report observation of the electroweak production of single top quarks in pp collisions at s=1.96 TeV based on 2.3 fb(-1) of data collected by the D0 detector at the Fermilab Tevatron Collider. Using events containing an isolated electron or muon and missing transverse energy, together with jets originating from the fragmentation of b quarks, we measure a cross section of sigma(pp -> tb+X,tqb+X)=3.94 +/- 0.88 pb. The probability to measure a cross section at this value or higher in the absence of signal is 2.5x10(-7), corresponding to a 5.0 standard deviation significance for the observation.

Precise measurement of the e+e-→π+π-(γ) cross section with the initial-state radiation method at BABAR

Abstract: A precise measurement of the cross section for the process e^+e^- → K^+K^-(γ) from threshold to an energy of 5 GeV is obtained with the initial-state radiation (ISR) method using 232 fb^(-1) of data collected with the BABAR detector at e^+e^- center-of-mass energies near 10.6 GeV. The measurement uses the effective ISR luminosity determined from the e^+e^- → μ^+μ^-(γ)γ_(ISR) process with the same data set. The corresponding lowest-order contribution to the hadronic vacuum polarization term in the muon magnetic anomaly is found to be a_μ^(KK,LO)=(22.93 ± 0.18_(stat) ± 0.22_(syst))×10^(-10). The charged kaon form factor is extracted and compared to previous results. Its magnitude at large energy significantly exceeds the asymptotic QCD prediction, while the measured slope is consistent with the prediction.

Observation of a kilogram-scale oscillator near its quantum ground state

Abstract: We introduce a novel cooling technique capable of approaching the quantum ground state of a kilogram-scale system—an interferometric gravitational wave detector. The detectors of the Laser Interferometer Gravitational-wave Observatory (LIGO) operate within a factor of 10 of the standard quantum limit (SQL), providing a displacement sensitivity of 10−18 m in a 100 Hz band centered on 150 Hz. With a new feedback strategy, we dynamically shift the resonant frequency of a 2.7 kg pendulum mode to lie within this optimal band, where its effective temperature falls as low as 1.4 μK, and its occupation number reaches about 200 quanta. This work shows how the exquisite sensitivity necessary to detect gravitational waves can be made available to probe the validity of quantum mechanics on an enormous mass scale.

Evidence for X(3872)→ψ(2S)γ in B±→X(3872) K± Decays and a Study of B→cc̄γK

Abstract: In a search for B --> ccbar gamma K decays with the BaBar detector, where ccbar includes J/psi and psi(2S), and K includes K+, Ks, and K*(892), we find evidence for X(3872) --> J/psi gamma and X(3872) --> psi(2S) gamma with 3.6 sigma and 3.5 sigma significance, respectively. We measure the product of branching fractions BR(B+ --> X(3872) K+) x BR(X(3872) --> J/psi gamma) = (2.8 +/- 0.8(stat.) +/- 0.2(syst.)) x 10^(-6) and BR(B+ --> X(3872) K+) x BR(X(3872) --> psi(2S) gamma) = (9.9 +/- 2.9(stat.) +/- 0.6(syst.)) x 10^(-6).

Search for Dimuon Decays of a Light Scalar Boson in Radiative Transitions Υ→γA0

Abstract: We search for evidence of a light scalar boson in the radiative decays of the {Upsilon}(2S) and {Upsilon}(3S) resonances: {Upsilon}(2S, 3S) {yields} {gamma}A{sup 0}, A{sup 0} {yields} {mu}{sup +}{mu}{sup -}. Such a particle appears in extensions of the Standaard Model, where a light CP-odd Higgs boson naturally couples strongly to b-quarks. We find no evidence for such processes in the mass range 0.212 {<=} m{sub A{sup 0}} {<=} 9.3 GeV in the samples of 99 x 10{sup 6} {Upsilon}(2S) and 122 x 10{sup 6} {Upsilon}(3S) decays collected by the BABAR detector at the PEP-II B-factory and set stringent upper limits on the effective coupling of the b quark to the A{sup 0}. We also limit the dimuon branching fraction of the {eta}{sub b} meson: {Beta}({eta}{sub b} {yields} {mu}{sup +}{mu}{sup -}) < 0.9% at 90% confidence level.

Einstein@Home search for periodic gravitational waves in LIGO S4 data

Abstract: A search for periodic gravitational waves, from sources such as isolated rapidly spinning neutron stars, was carried out using 510 h of data from the fourth LIGO science run (S4). The search was for quasimonochromatic waves in the frequency range from 50 to 1500 Hz, with a linear frequency drift f˙ (measured at the solar system barycenter) in the range -f/τ

Combination of tt̄ cross section measurements and constraints on the mass of the top quark and its decays into charged Higgs bosons

Abstract: We combine measurements of the top quark pair production cross section in p (p) over bar collisions in the l + jets, ll, and tau l final states ( where l is an electron or muon) at a center of mass energy of root s = 1.96 TeV in 1 fb(-1) of data collected with the D0 detector. For a top quark mass of 170 GeV/c(2), we obtain sigma(t (t) over bar) = 8.18(-0.87)(+0.98) pb in agreement with the theoretical prediction. Based on predictions from higher order quantum chromodynamics, we extract a mass for the top quark from the combined t (t) over bar cross section, consistent with the world average of the top quark mass. In addition, the ratios of t (t) over bar cross sections in different final states are used to set upper limits on the branching fractions B(t -> H(+)b -> tau(+) vb) and B(t -> H(+)b -> c (s) over barb) as a function of the charged Higgs boson mass.

Measurement of time-dependent CP asymmetry in B0→cc̄K(*)0 decays

Abstract: We present updated measurements of time-dependent CP asymmetries in fully reconstructed neutral B decays containing a charmonium meson. The measurements reported here use a data sample of (465 +/- 5)x10(6) Upsilon(4S)-> B B decays collected with the BABAR detector at the PEP-II asymmetric energy e(+)e(-) storage rings operating at the SLAC National Accelerator Laboratory. The time-dependent CP asymmetry parameters measured from J psi K-S(0), J psi K-L(0), psi(2S)K-S(0), eta K-c(S)0, chi K-c1(S)0, and J/psi K-*(892)(0) decays are: C-f=0.024 +/- 0.020(stat)+/- 0.016(syst) and -eta S-f(f)=0.687 +/- 0.028(stat)+/- 0.012(syst).

Study of DsJ decays to D*K in inclusive e+e- interactions

Abstract: We observe the decays D*_(s1)(2710)^+ → D*K and D*_(sJ)(2860)^+ → D*K and measure their branching fractions relative to the DK final state. We also observe, in the D*K mass spectrum, a new broad structure at a mass of (3044 ± 8_(stat)(^(+30)_(-5))_(syst)) MeV/c^2 having a width Γ =(239 ± 35_(stat)(^(+46)_(-42))_(syst)) MeV. To obtain this result we use 470 fb^(-1) of data recorded by the BABAR detector at the PEP-II asymmetric-energy e^+e^- storage rings at the Stanford Linear Accelerator Center running at center-of-mass energies near 10.6 GeV.

Measurement of Dijet Angular Distributions at s=1.96TeV and Searches for Quark Compositeness and Extra Spatial Dimensions

Abstract: We present the first measurement of dijet angular distributions in ppbar collisions at sqrt{s}=1.96TeV at the Fermilab Tevatron Collider. The measurement is based on a dataset corresponding to an integrated luminosity of up to 0.7fb-1 collected with the D0 detector. Dijet angular distributions have been measured over a range of dijet masses, from 0.25TeV to above 1.1TeV. The data are in good agreement with the predictions of perturbative QCD and are used to constrain new physics models including quark compositeness, large extra dimensions, and TeV-1 scale extra dimensions. For all models we set the most stringent direct limits to date.

Angular distributions in the decay B -> K*l(+)l(-)

Abstract: We use a sample of 384 million BBbar events collected with the Babar detector at the PEP-II e+e- collider to study angular distributions in the rare decays B -> K* l+l-, where l+l- is either e+e- or mu+mu-. For low dilepton invariant masses, m(l+l-) 3.2$ GeV/c^2, we measure AFB=0.76 (+0.52,-0.32) +/- 0.07 FL=0.71 (+0.20,-0.22) +/- 0.04.

Direct CP, Lepton Flavor and Isospin Asymmetries in the Decays B->K(*)l+l-

Abstract: We measure branching fractions and integrated rate asymmetries for the rare decays B -> K((*))l(+)l(-), where l(+)l(-) is either e(+)e(-) or mu(+)mu(-), using a sample of 384x10(6) BB events collected with the BABAR detector at the PEP-II e(+)e(-) collider. We find no evidence for direct CP or lepton-flavor asymmetries. However, for dilepton masses below the J/psi resonance, we find evidence for unexpectedly large isospin asymmetries in both B -> Kl(+)l(-) and B -> K(*)l(+)l(-) which differ, respectively, by 3.2 sigma and 2.7 sigma, including systematic uncertainties, from the standard model expectations.

Dalitz Plot Analysis of B+- --> pi+-pi+-pi-+ Decays

Abstract: We present a Dalitz plot analysis of charmless B-+/- decays to the final state pi(+/-)pi(+/-)pi(-/+) using a sample of (465 +/- 5)x10(6) B(B)over bar pairs collected by the BABAR experiment at root s=10.58 GeV. We measure the branching fractions B(B-+/-->pi(+/-)pi(+/-)pi(-/+))=(15.2 +/- 0.6 +/- 1.2 +/- 0.4)x10(-6), B(B-+/-->rho(0)(770)pi(+/-))=(8.1 +/- 0.7 +/- 1.2(-1.1)(+0.4))x10(-6), B(B-+/--> f(2)(1270)pi(+/-))=(1.57 +/- 0.42 +/- 0.16(-0.19)(+0.53))x10(-6), and B(B-+/-->pi(+/-)pi(+/-)pi(-/+) nonresonant)=(5.3 +/- 0.7 +/- 0.6(-0.5)(+1.1))x10(-6), where the uncertainties are statistical, systematic, and model-dependent, respectively. Measurements of branching fractions for the modes B-+/-->rho(0)(1450)pi(+/-) and B-+/--> f(0)(1370)pi(+/-) are also presented. We observe no significant direct CP asymmetries for the above modes, and there is no evidence for the decays B-+/--> f(0)(980)pi(+/-), B-+/-->chi(c0)pi(+/-), or B-+/-->chi(c2)pi(+/-).

Expected performance of the ATLAS experiment - detector, trigger and physics

Abstract: A detailed study is presented of the expected performance of the ATLAS detector. The reconstruction of tracks, leptons, photons, missing energy and jets is investigated, together with the performance of b-tagging and the trigger. The physics potential for a variety of interesting physics processes, within the Standard Model and beyond, is examined. The study comprises a series of notes based on simulations of the detector and physics processes, with particular emphasis given to the data expected from the first years of operation of the LHC at CERN.

Measurement of the e(+)e(-) -> b(b)over-bar cross section between root s=10.54 and 11.20 GeV

Abstract: We report e;{+}e;{-}-->bb[over ] cross section measurements by the BABAR experiment performed during an energy scan in the range of 10.54 to 11.20 GeV at the SLAC PEP-II e;{+}e;{-} collider. A total relative error of about 5% is reached in more than 300 center-of-mass energy steps, separated by about 5 MeV. These measurements can be used to derive precise information on the parameters of the Upsilon(10860) and Upsilon(11020) resonances. In particular we show that their widths may be smaller than previously measured.

Measurement of time-dependentCPasymmetry inB0→cc¯K(*)0decays

Abstract: Author(s): Aubert, B; Bona, M; Boutigny, D; Karyotakis, Y; Lees, JP; Poireau, V; Prudent, X; Tisserand, V; Zghiche, A; Garra Tico, J; Grauges, E; Lopez, L; Palano, A; Pappagallo, M; Eigen, G; Stugu, B; Sun, L; Abrams, GS; Battaglia, M; Brown, DN; Button-Shafer, J; Cahn, RN; Groysman, Y; Jacobsen, RG; Kadyk, JA; Kerth, LT; Kolomensky, YG; Kukartsev, G; Lopes Pegna, D; Lynch, G; Mir, LM; Orimoto, TJ; Osipenkov, IL; Ronan, MT; Tackmann, K; Tanabe, T; Wenzel, WA; Del Amo Sanchez, P; Hawkes, CM; Watson, AT; Koch, H; Schroeder, T; Walker, D; Asgeirsson, DJ; Cuhadar-Donszelmann, T; Fulsom, BG; Hearty, C; Mattison, TS; McKenna, JA; Khan, A; Saleem, M; Teodorescu, L; Blinov, VE; Bukin, AD; Druzhinin, VP; Golubev, VB; Onuchin, AP; Serednyakov, SI; Skovpen, YI; Solodov, EP; Todyshev, KY; Bondioli, M; Curry, S; Eschrich, I; Kirkby, D; Lankford, AJ; Lund, P; Mandelkern, M; Martin, EC; Stoker, DP; Abachi, S; Buchanan, C; Foulkes, SD; Gary, JW; Liu, F; Long, O; Shen, BC; Vitug, GM; Zhang, L; Paar, HP; Rahatlou, S; Sharma, V; Berryhill, JW; Campagnari, C; Cunha, A | Abstract: We present a preliminary measurement of the time-dependent CP asymmetry in B0 → K *0 (K 0 S π 0 )γ decays based on 431 × 106 γ(4S) → BB decays collected with the BABAR detector at the PEP-II asymmetric-energy e + e - collider at SLAC. In a sample containing 316±22 signal events we measure SK * = -0.08 ± 0.31 ± 0.05 and CK * γ = -0.15 ± 0.17 ± 0.03. The uncertainties are statistical and systematic, respectively.

Study ofDsJdecays toD*Kin inclusivee+e−interactions

Abstract: We observe the decays ${D}_{s1}^{*}(2710{)}^{+}\ensuremath{\rightarrow}{D}^{*}K$ and ${D}_{sJ}^{*}(2860{)}^{+}\ensuremath{\rightarrow}{D}^{*}K$ and measure their branching fractions relative to the $DK$ final state. We also observe, in the ${D}^{*}K$ mass spectrum, a new broad structure at a mass of $(3044\ifmmode\pm\else\textpm\fi{}{8}_{\mathrm{stat}}(\genfrac{}{}{0}{}{+30}{\ensuremath{-}5}{)}_{\mathrm{syst}})\text{ }\text{ }\mathrm{MeV}/{c}^{2}$ having a width $\ensuremath{\Gamma}=(239\ifmmode\pm\else\textpm\fi{}{35}_{\mathrm{stat}}(\genfrac{}{}{0}{}{+46}{\ensuremath{-}42}{)}_{\mathrm{syst}})\text{ }\text{ }\mathrm{MeV}$. To obtain this result we use $470\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of data recorded by the BABAR detector at the PEP-II asymmetric-energy ${e}^{+}{e}^{\ensuremath{-}}$ storage rings at the Stanford Linear Accelerator Center running at center-of-mass energies near 10.6 GeV.

Determination of the strong coupling constant from the inclusive jet cross section in pp̄ collisions at s=1.96TeV

Abstract: We determine the strong coupling constant alpha(s) and its energy dependence from the p(T) dependence of the inclusive jet cross section in pp collisions at s=1.96 TeV. The strong coupling constant is determined over the transverse momentum range 50 < p(T)< 145 GeV. Using perturbative QCD calculations to order O(alpha(3)(s)) combined with O(alpha(4)(s)) contributions from threshold corrections, we obtain alpha(s)(M-Z)=0.1161(-0.0048)(+0.0041). This is the most precise result obtained at a hadron-hadron collider.

Search for Long-Lived Charged Massive Particles with the D0 Detector

Abstract: We search for long-lived charged massive particles using 1.1 fb(-1) of data collected by the D0 detector at the Fermilab Tevatron pp Collider. Time-of-flight information is used to search for pair produced long-lived tau sleptons, gauginolike charginos, and Higgsino-like charginos. We find no evidence of a signal and set 95% C.L. cross section upper limits for staus, which vary from 0.31 to 0.04 pb for stau masses between 60 and 300 GeV. We also set lower mass limits of 206 GeV (171 GeV) for pair produced charged gauginos (Higgsinos).

Evidence for the ηb(1S) Meson in Radiative Υ(2S) Decay

Abstract: We have performed a search for the eta_b(1S) meson in the radiative decay of the Upsilon(2S) resonance using a sample of 91.6 million Upsilon(2S) events recorded with the BABAR detector at the PEP-II B factory at the SLAC National Accelerator Laboratory. We observe a peak in the photon energy spectrum at E_gamma = 610.5 {+4.5} {-4.3} (stat) +/- 1.8 (syst) MeV, corresponding to an eta_b(1S) mass of 9392.9 {+4.6} {-4.8} (stat) +/- 1.9 (syst) MeV/c^2. The branching fraction for the decay Upsilon(2S) --> gamma eta_b(1S) is determined to be (4.2 {+1.1} {-1.0} (stat) +/- 0.9 (syst)) x 10^(-4). The ratio B(Upsilon(2S) --> gamma eta_b(1S))/B(Upsilon(3S) --> gamma eta_b(1S)) = 0.89 {+0.25} {-0.23} (stat) {+0.12}{-0.16} (syst) is consistent with the ratio expected for magnetic dipole transitions to the eta_b(1S) meson.

Exclusive initial-state-radiation production of the DD¯, D*D¯, and D*D¯* systems

Abstract: We perform a study of the exclusive production of in initial-state-radiation events, from e(+)e(-) annihilations at a center-of-mass energy near 10.58 GeV, to search for charmonium and possible new resonances. The data sample corresponds to an integrated luminosity of 384 fb(-1) and was recorded by the BABAR experiment at the PEP-II storage rings. The D (D) over bar, D*(D) over bar, D*(D) over bar* mass spectra show clear evidence of several psi resonances. However, there is no evidence for Y(4260) -> D*(D) over bar or Y(4260) -> D*(D) over bar*.

Measurements of the semileptonic decays (B)over-bar -> Dl(nu)over-bar and (B)over-bar -> D*l(nu)over-bar using a global fit to DXl(nu)over-bar final states

Abstract: Semileptonic (B) over bar decays to DXl (nu) over bar (l = e or mu) are selected by reconstructing D(0)l and D(+)l combinations from a sample of 230 x 10(6) Y(4S) --> B (B) over bar decays recorded with the BABAR detector at the PEP-II e(+)e(-) collider at SLAC. A global fit to these samples in a three-dimensional space of kinematic variables is used to determine the branching fractions B(B- --> D(0)l (nu) over bar = (2.34 +/- 0.03 +/- 0.13)% and B(B- --> D*(0)l (nu) over bar) = (5.40 +/- 0.02 +/- 0.21)% where the errors are statistical and systematic, respectively. The fit also determines form-factor parameters in a parametrization based on heavy quark effective theory, resulting in rho(2)(D) = 1.20 +/- 0.04 +/- 0.07 for (B) over bar --> Dl (nu) over bar and rho(2)(D*) = 1.22 +/- 0.02 +/- 0.07 for (B) over bar --> D*(0)l (nu) over bar. These values are used to obtain the product of the Cabibbo-Kobayashi-Maskawa matrix element |V-cb| times the form factor at the zero recoil point for both (B) over bar --> Dl (nu) over bar decays, G(1)|V-cb| = (43.1 +/- 0.8 +/- 2.3) x 10(-3), and for (B) over bar --> D*l (nu) over bar decays, F(1)|V-cb| = (35.9) +/- 0.2 +/- 1.2) x 10(-3).

Measurement of the lifetime of the Bc± meson in the semileptonic decay channel

Abstract: Using approximately 1.3 fb(-1) of data collected by the D0 detector between 2002 and 2006, we measure the lifetime of the B-c(+/-) meson in the B-c(+/-)-> J/psi mu(+/-)+X final state. A simultaneous unbinned likelihood fit to the J/psi+mu invariant mass and lifetime distributions yields a signal of 881 +/- 80(stat) candidates and a lifetime measurement of tau(B-c(+/-))=0.448(-0.036)(+0.038)(stat)+/- 0.032(syst) ps.

Search for resonant pair production of neutral long-lived particles decaying to bb̄ in pp̄ collisions at s=1.96TeV

Abstract: We report on a first search for resonant pair production of neutral long-lived particles (NLLP) which each decay to a b (b) over bar pair, using 3.6 fb(-1) of data recorded with the D0 detector at the Fermilab Tevatron collider. We search for pairs of displaced vertices in the tracking detector at radii in the range 1.6-20 cm from the beam axis. No significant excess is observed above background, and upper limits are set on the production rate in a hidden-valley benchmark model for a range of Higgs boson masses and NLLP masses and lifetimes.

Time-dependent amplitude analysis of B0 -> KS0π+π-

Abstract: We perform a time-dependent amplitude analysis of B^0→K_S^0π^+π^- decays to extract the CP violation parameters of f_0(980)K_S^0 and ρ^0(770)K_S^0 and the direct CP asymmetry of K^(*+)(892)π^-. The results are obtained from a data sample of (383±3)×10^6 BB decays, collected with the BABAR detector at the PEP-II asymmetric–energy B factory at SLAC. We find two solutions, with an equivalent goodness-of-fit. Including systematic and Dalitz plot model uncertainties, the combined confidence interval for values of the CP parameter β_(eff) in B^0 decays to f_0(980)K_S^0 is 18°<β_(eff)<76° at 95% confidence level (C.L). CP conservation in B^0 decays to f_0(980)K_S^0 is excluded at 3.5 standard deviations including systematic uncertainties. For B^0 decays to ρ^0(770)K_S^0, the combined confidence interval is -9°<β_(eff)<57° at 95% C.L. In decays to K^(*+)(892)π^- we measure the direct CP asymmetry to be A_(CP)=-0.20±0.10±0.01±0.02. The measured phase difference (including B^0B ^0 mixing) between decay amplitudes of B^0→K^(*+)(892)π^- and B ^0→K^(*-)(892)π^+, excludes the interval -137°<ΔΦ(K^(*+)(892)π^-)<-5° at 95% C.L.

Measurement of D0-D̄0 mixing using the ratio of lifetimes for the decays D0→K-π+ and K+K-

Abstract: We measure the rate of D^0-D ^0 mixing with the observable y_(CP)=(τ_(Kπ)/τ_(KK))-1, where τ_(KK) and τ_(Kπ) are, respectively, the mean lifetimes of CP-even D^0→K^+K^- and CP-mixed D^0→K^-π^+ decays, using a data sample of 384 fb^(-1) collected by the BABAR detector at the SLAC PEP-II asymmetric-energy B Factory. From a sample of D^0 and D ^0 decays where the initial flavor of the decaying meson is not determined, we obtain y_(CP)=[1.12±0.26(stat)±0.22(syst)]%, which excludes the no-mixing hypothesis at 3.3σ, including both statistical and systematic uncertainties. This result is in good agreement with a previous BABAR measurement of y_(CP) obtained from a sample of D^(*+)→D^0π^+ events, where the D^0 decays to K^-π^+, K^+K^-, and π^+π^-, which is disjoint with the untagged D^0 events used here. Combining the two results taking into account statistical and systematic uncertainties, where the systematic uncertainties are assumed to be 100% correlated, we find y_(CP)=[1.16±0.22(stat)±0.18(syst)]%, which excludes the no-mixing hypothesis at 4.1σ.

Search for a Low-Mass higgs boson in Υ(3S)→γA0, A0→τ+τ- at BABAR

Abstract: We search for a light Higgs boson, $A^0$, in the radiative decay $\Upsilon(3S)\to\gamma A^0$, $A^0\to\tau^+\tau^-$, $\tau^+\to e^+ u_e \overline{ u}_{\tau}$ or $\tau^+\to \mu^+ u_{\mu} \overline{ u}_{\tau}$. The data sample contains 122 million $\Upsilon(3S)$ events recorded with the \babar detector. We find no evidence for a narrow structure in the studied $\tau^+\tau^-$ invariant mass region of $4.03(1.5-16)\times 10^{-5}$ across the $m_{\tau^+\tau^-}$ range. We also set a 90% C.L. upper limit on the $\tau^+\tau^-$-decay of the $\eta_b$ at ${\mathcal{B}}(\eta_b\to \tau^+\tau^-)<8%$.

Search for charged Higgs bosons in decays of top quarks

Abstract: We present a search for charged Higgs bosons in decays of top quarks, in the mass range 80 tau(+)nu(tau) (and its charge conjugate). Using 0.9 fb(-1) of lepton + jets data collected with the D0 detector at the Fermilab Tevatron p (p) over bar collider, operating at a center of mass energy root s = 1.96 TeV, we find no evidence for a H+/- signal. Hence we exclude branching ratios B(t -> H(+)b) > 0.24 for m(H+) 80 GeV and B(t -> H(+)b) > 0.19 for m(H+) = 155 GeV at the 95% C.L.