Observation of the decay B- → D(s)((*)+) K- ℓ- ν(ℓ)

We report the observation of the decay B- → D(s)((*)+) K- ?- ν(?) based on 342 fb(-1) of data collected at the Υ(4S) resonance with the BABAR detector at the PEP-II e+ e- storage rings at SLAC. A simultaneous fit to three D(s)(+) decay chains is performed to extract the signal yield from measurements of the squared missing mass in the B meson decay. We observe the decay B- → D(s)((*)+) K- ?- ν(?) with a significance greater than 5 standard deviations (including systematic uncertainties) and measure its branching fraction to be B(B- → D(s)((*)+) K- ?- ν(?)) = [6.13(-1.03)(+1.04)(stat)±0.43(syst)±0.51(B(D(s)))]×10(-4), where the last error reflects the limited knowledge of the D(s) branching fractions.     

Determination of f(s)/f(d) for 7 TeV pp collisions and measurement of the B0→D-K+ branching fraction

The relative abundance of the three decay modes B(0)→D(-)K(+), B(0)→D(-)π(+), and B(s)(0)→D(s)(-)π(+) produced in 7 TeV pp collisions at the LHC is determined from data corresponding to an integrated luminosity of 35 pb(-1). The branching fraction of B(0)→D(-)K(+) is found to be B(B(0)→D(-)K(+)) = (2.01 ± 0.18(stat) ± 0.14(syst)) × 10(-4). The ratio of fragmentation fractions f(s)/f(d) is determined through the relative abundance of B(s)(0)→D(s)(-)π(+) to B(0)→D(-)K(+) and B(0)→D(-)π(+), leading to f(s)/f(d) = 0.253 ± 0.017 ± 0.017 ± 0.020, where the uncertainties are statistical, systematic, and theoretical, respectively.     

K→(ππ)(I=2) decay amplitude from lattice QCD

We report on the first realistic ab initio calculation of a hadronic weak decay, that of the amplitude A(2) for a kaon to decay into two π mesons with isospin 2. We find ReA(2)=(1.436±0.063(stat)±0.258(syst))10(-8) GeV in good agreement with the experimental result and for the hitherto unknown imaginary part we find ImA(2)=-(6.83±0.51(stat)±1.30(syst))10(-13) GeV. Moreover combining our result for ImA(2) with experimental values of ReA(2), ReA(0), and ε'/ε, we obtain the following value for the unknown ratio ImA(0)/ReA(0) within the standard model: ImA(0)/ReA(0)=-1.63(19)(stat)(20(syst)×10(-4). One consequence of these results is that the contribution from ImA(2) to the direct CP violation parameter ε' (the so-called Electroweak Penguin contribution) is Re(ε'/ε)(EWP)=-(6.52±0.49(stat)±1.24(syst))×10(-4). We explain why this calculation of A(2) represents a major milestone for lattice QCD and discuss the exciting prospects for a full quantitative understanding of CP violation in kaon decays.     

Evidence for direct CP violation in B±→ηh± and observation of B0→ηK0

We report measurements of the branching fractions and CP asymmetries for B(±)→ηh(±) (h=K or π) and the observation of the decay B(0)→ηK(0) from the final data sample of 772×10(6) B ?B pairs collected with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. The measured branching fractions are B(B(±)→ηK(±))=(2.12±0.23±0.11)×10(-6), B(B(±)→ηπ(±))=(4.07±0.26±0.21)×10(-6), and B(B(0)→ηK(0))=(1.27(-0.29)(+0.33)±0.08)×10(-6), where the last decay is observed for the first time with a significance of 5.4 standard deviations (σ). We also find evidence for CP violation in the charged B modes, A(CP)(B(±)→ηK(±))=-0.38±0.11±0.01 and A(CP)(B(±)→ηπ(±))=-0.19±0.06±0.01 with significances of 3.8 σ and 3.0 σ, respectively. For all measurements, the first and second uncertainties are statistical and systematic, respectively.     

Cs(6D_J)+(H_2,H_e)的反应与非反应碰撞能量转移

在样品池条件下,利用原子荧光光谱方法,测量了Cs(6DJ)与H2,He碰撞中的反应与非反应能量转移截面.利用脉冲激光886nm线双光子激发Cs(6S)到Cs(6D3/2)态,原子荧光中除含有6D3/2→6P的直接荧光外,还含有6D5/2→6P的转移荧光.利用三能级模型的速率方程分析,在不同的He和H2密度下,分别测垦直接荧光与转移荧光的时间积分荧光强度比,得到了6D3/2与H2和He碰撞的精细结构转移截面分别为σ=(55±13)×10-16和(16±4)×10-16 cm2,同时确定了6D5/2与H2和He的碰撞猝灭速率系数.6D5/2态与H2的碰撞猝灭速率系数比6D5/2与He的大,它是反应与非反应速率系数之和,利用实验数据确定非反应速率系数为6.3×10-10 cm3·s-1,得到6D5/2与H2的反应截面为(2.0±0.8)×10-16 cm2.利用不同H2(或He)密度下6D5/2→6P3/2时间积分荧光强度,得到6D3/2与H2反应截面为(4.0±1.6)×10-16 cm2,6D3/2与H2反应的活性大于6D5/2.     

First observation of the decays B(0) → D(+)K(-)π(+)π(-) and B(-) → D(0)K(-)π(+)π(-)

First observations of the Cabibbo-suppressed decays B(0) → D(+)K(-)π(+)π(-) and B(-) → D(0)K(-)π(+)π(-) are reported using 35 pb(-1) of data collected with the LHCb detector. Their branching fractions are measured with respect to the corresponding Cabibbo-favored decays, from which we obtain B(B(0) → D(+)K(-)π(+)π(-))/B(B(0) → D(+)π(-)π(+)π(-))=(5.9±1.1±0.5)×10(-2) and B(B(-) → D(0)K(-)π(+)π(-))/B(B(-) → D(0)π(-)π(+)π(-))=(9.4±1.3±0.9)×10(-2), where the uncertainties are statistical and systematic, respectively. The B(-) → D(0)K(-)π(+)π(-) decay is particularly interesting, as it can be used in a similar way to B(-) → D(0)K(-) to measure the Cabibbo-Kobayashi-Maskawa phase γ.     

Cross section and parity-violating spin asymmetries of W± boson production in polarized p + p collisions at sqrt[s] = 500 GeV

Large parity-violating longitudinal single-spin asymmetries A(L)(e+) = -0.86(-0.14) (+0.30) and A(L)(e-) = 0.88(-0.71) (+0.12) are observed for inclusive high transverse momentum electrons and positrons in polarized p+p collisions at a center-of-mass energy of sqrt[s] = 500 GeV with the PHENIX detector at RHIC. These e± come mainly from the decay of W± and Z0 bosons, and their asymmetries directly demonstrate parity violation in the couplings of the W± to the light quarks. The observed electron and positron yields were used to estimate W± boson production cross sections for the e± channels of σ(pp → W+ X) × BR(W+ → e+ ν(e)) = 144.1 ± 21.2(stat)(-10.3) (+3.4) (syst) ± 21.6(norm) pb, and σ(pp → W- X) × BR(W- → e- ν[over ˉ](e)) = 31.7 ± 12.1(stat)(-8.2) (+10.1) (syst) ± 4.8(norm) pb.     

Cs(6DJ)+Cs(6S1/2)非弹性碰撞转移截面的测定

在9×1014～2.1×1015cm-3 Cs密度范围内,利用脉冲激光双光子激发Cs(6S1/2)到Cs(6D5/2)态,使用原子荧光光谱方法,通过三能级模型的速率方程分析,由对直接荧光和转移荧光的时间积分强度的测量,得到6D5/2→6D3/2精细结构转移截面为(2.1±0.4)×10-14cm2,而6D3/2态向6D以外态的转移截面为(1.6±0.4)×10-14cm2,它应是过程Cs(6 D3/2)+Cs(6S)→Cs(6P)+Cs(6P),6D3/2→7P3/2和6D3/2→7 P1/2碰撞转移截面之和.第二个实验可以得到6 D3/2→7P3/2和6D3/2→7 P1/2的碰撞转移截面.在1×1012～6×1012cm-3的低密度Cs蒸气中,激光双光子激发6S至6D3/2或6D5/2态,测量6DJ→6PJ'与7PJ"→6S1/2的时间积分荧光强度比,得到6D3/2→7P1/2与6D5/2→7R3/2的碰撞转移截面分别为(7.6±2.4)×10-15cm2与(1.6±0.5)×10-15cm2.由此得到碰撞能量合并的逆过程即[Cs(6D3/2)+Cs(6S1/2)→Cs(6P)+Cs(6P)]的转移截面为(1.3±0.4)×10-14cm2.     

基于2D微电子机械系统(MEMS)镜全向激光雷达光学系统设计

为了满足全向激光探测的需求,提出一种基于2DMEMS镜扫描的激光雷达结构。激光器通过1×6高速光开关分时地给6个扫描子系统提供光信号,6个扫描子系统探测视场叠加起来可实现360°激光探测。每个扫描子系统的扫描范围为60°×30°,其中包含一个扩展MEMS镜扫描角度的发射光学天线和一个大视场有增益的接收光学天线。发射光学天线将MEMS镜±10°的扫描角扩展到±30°,发散度小于0.2mrad;接收视场内的激光波经过接收天线在探测器上所成的半像高小于1mm,接收增益为3.65。通过计算修正后的激光雷达方程可得到发射功率20 W的激光束在工作距离100 m内的回波功率≥1 nW,结果表明该光学系统可适用于激光雷达系统。     

Residual symmetries for neutrino mixing with a large θ13 and nearly maximal δD

The residual Z(2)(s)(k) and Z(2)(s)(k) symmetries induce a direct and unique phenomenological relation with θx (≡ θ13) expressed in terms of the other two mixing angles θs(≡ θ12) and θa(≡ θ23) and the Dirac CP phase δD. Z(2)(s)(k) predicts a θx probability distribution centered around 3°-6° with an uncertainty of 2°-4°, while those from Z(2)(s)(k) are approximately a factor of 2 larger. Either result fits the T2K, MINOS, and Double Chooz measurements. Alternately, a prediction for the Dirac CP phase δD results in a peak at ± 74° (± 106°) for Z(2)(s)(k) or ± 123° (± 57°) for Z(2)(s)(k) which is consistent with the latest global fit. We also give a distribution for the leptonic Jarlskog invariant Jν which can provide further tests from measurements at T2K and NOνA.     

Measurement of polarization and search for CP violation in B(s)0→φφ decays

We present the first measurement of polarization and CP-violating asymmetries in a B(s)(0) decay into two light vector mesons, B(s)(0)→φφ, and an improved determination of its branching ratio using 295 decays reconstructed in a data sample corresponding to 2.9 fb(-1) of integrated luminosity collected by the CDF experiment at the Fermilab Tevatron collider. The fraction of longitudinal polarization is determined to be f(L)=0.348±0.041(stat)±0.021(syst), and the branching ratio B(B(s)(0)→φφ)=[2.32±0.18(stat)±0.82(syst)]×10(-5). Asymmetries of decay angle distributions sensitive to CP violation are measured to be A(u)=-0.007±0.064(stat)±0.018(syst) and A(v)=-0.120±0.064(stat)±0.016(syst).     

Evidence for heavy hyperhydrogen (Λ)(6)h

Evidence for the neutron-rich hypernucleus (Λ)(6)H is presented from the FINUDA experiment at DAΦNE, Frascati, studying (π+,π-) pairs in coincidence from the K(stop)(-) + (6)Li →(Λ)(6)H + π+ production reaction followed by (Λ)(6)H → (6)He + π- weak decay. The production rate of (Λ)(6) undergoing this two-body π- decay is determined to be (2.9 ± 2.0) × 10(-6)/K(stop)(-). Its binding energy, evaluated jointly from production and decay, is BΛ((Λ)(6)H) = (4.0 ± 1.1) MeV with respect to (5)H+Λ. A systematic difference of (0.98 ± 0.74) MeV between BΛ values derived separately from decay and from production is tentatively assigned to the (Λ)(6)H 0(g.s.)(+) → 1+ excitation.     

K(6S)+H2→K(4D)+H2的碰撞能量转移

激光双光子激发K原子至6s或4D态,测鼍了K(6S,4D)与H2的碰撞转移截面.池温在413K,H2气压在4～40 Pa范围内,K(6S,4D)-K的碰撞效应可略去.在激发6S态的情况下,记录6S→4P时间分辨荧光信号,从荧光强度的对数描绘出的直线斜率得到6S态的有效寿命,而4D态的布居随H2的增加而增加,因此引起4D→4P跃迁谱线的增强.在激发4D态的情况下,采用类似方法得到4D态的有效寿命,由Stern Volmet方程,测得6S和4D态的辐射寿命分别为(97±15)ns和(300±45)ns.激发态K原子总的碰撞去佰居截面为(1.6±0.3)×10-14cm2(对6S态)和(40±6)×10-16cm2(对4D态).该总截面中包含向K原子激发态的非反应碰撞转移截面以及与H2反应生成KH的反应截面.激发6S态,测量4D→4P的时间积分荧光强度随H2气压的变化,得到6S→4D的碰撞转移截面为(1.4±0.3)×10-14cm2.由此得到结论:K(6S)态主要是通过物理猝灭到K(4D)态,虽然在K(6S)+H2的碰撞中,观察到了由于化学反应生成的KH的存在.     

ηπ+ π- resonant structure around 1.8 GeV/c(2) and η(1405) in J/ψ → ωηπ+ π-

We present results of a study of the decay J/ψ → ωηπ+ π- using a sample of (225.2 ± 2.8) × 10(6) J/ψ events collected by the BESIII detector, and report the observation of a new process J/ψ → ωX(1870) with a statistical significance of 7.2σ, in which X(1870) decays to a(0)(±)(980)π±. Fitting to ηπ+ π- mass spectrum yields a mass M = 1877.3 ± 6.3(stat)(-7.4)(+3.4)(syst) MeV/c(2), a width Γ = 57 ± 12(stat)(-4)(+19)(syst) MeV/c(2), and a product branching fraction B(J/ψ → ωX) × B(X→a(0)(±)(980)π±) × B(a(0) (±)(980) → ηπ±) = [1.50 ± 0.26(stat)(-0.36)(+0.72) (syst)] × 10(-4). Signals for J/ψ → ωf(1)(1285) and J/ψ → ω η(1405) are also clearly observed and measured.     

高位K2(1Λg) 与基态原子的碰撞转移

在K原子密度约为0.5～5×1016cm-3的样品池中,脉冲激光710 nm线双光子激发K2基态到高位1Λg态,研究了K2(1Λg)+ K(4S)碰撞转移过程.K原子密度由测量KD2线蓝翼对白光的吸收得到.测量不同K密度下1Λg态发射的时间分辨荧光强度,它是一条指数衰减曲线,由此得到1Λg态的有效寿命,从描绘出的有效寿命倒数与K原子密度关系直线的斜率得到1Λg态总的碰撞猝灭截面为(2.1±0.2)×10-14cm2,从截距得到的辐射寿命为(22±2)ns.测量了K的6S →4P3/2和4D→4P3/2在不同K密度下的时间积分荧光强度,得到了K2(1Λg)+K→K2(11∑ +g)+K(6S,4D)碰撞转移截面为(1.5±0.3)×10-15cm2(对转移到6S)和(8.5±3.0)×10-15cm2(对转移到4D).     

Charmonium results from BES

Using ～14×106ψ(2S) and ～58×106J/ψ data collected at BESⅡ/BEPC,the branching fraction of ψ(2S) →Ω+Ωˉ+ is measured with about 5σ statistical significance.The Λ electric dipole and Λ decay parameter are studied using the decay J/ψ→ΛΛ→ ppˉπ+π-.Using(106±3)×106 ψ(2S) decays collected at BESⅢ/BEPCⅡ,we have obtained some interesting physics results.The branching fractions of χcJ →π0π0,ηη are measured with precision improved.The mass and width of hc(11P1) state,together with the branching fractions of Br(ψ(2S) →π0hc) and Br(hc →γηc) are the first measurements.Surprisingly,the decays of χc1 →φφ,ωω,and ωφ are firstly observed in BESⅢ data.     

Observation of X(3872)→J/ψγ and search for X(3872)→ψ'γ in B decays

We report a study of B→(J/ψγ)K and B→(ψ'γ)K decay modes using 772×10? B ?B events collected at the Υ(4S) resonance with the Belle detector at the KEKB energy-asymmetric e(+)e(-) collider. We observe X(3872)→J/ψγ and report the first evidence for χ(c2)→J/ψγ in B→(X_{c ?cγ)K decays, while in a search for X(3872)→ψ'γ no significant signal is found. We measure the branching fractions, B(B(±)→X(3872)K(±))B(X(3872)→J/ψγ)=(1.78(-0.44)(+0.48)±0.12)×10(-6), B(B(±)→χ(c2)K(±))=(1.11(-0.34)(+0.36)±0.09)×10(-5), B(B(±)→X(3872)K(±))B(X(3872)→ψ'γ)<3.45×10? (upper limit at 90% C.L.), and also provide upper limits for other searches.     

Observation of the Ξ(b)(0) baryon

The observation of the bottom, strange baryon Ξ(b)(0) through the decay chain Ξ(b)(0)→Ξ(c)(+)π-, where ΞΞ(c)(+)→Ξ- π+ π+, Ξ-→Λπ-, and Λ→pπ-, is reported by using data corresponding to an integrated luminosity of 4.2 fb(-1) from pp collisions at square root(s)=1.96 TeV recorded with the Collider Detector at Fermilab. A signal of 25.3(-5.4)(+5.6) candidates is observed whose probability of arising from a background fluctuation is 3.6×10(-12), corresponding to 6.8 gaussian standard deviations. The Ξ(b)(0) mass is measured to be 5787.8±5.0(stat)±1.3(syst) MeV/c2. In addition, the Ξ(b)- baryon is observed through the process Ξ(b)-→Ξ(c)(0)π-, where Ξ(c)(0)→Ξ- π+, Ξ-→Λπ-, and Λ→pπ-.     

Rotation, the equivalence principle, and the Gravity Probe B experiment

The ultraprecise Gravity Probe B experiment measured the frame-dragging effect and geodetic precession on four quartz gyros. We use this result to test WEP II (weak equivalence principle II) which includes rotation in the universal free-fall motion. The free-fall E?tv?s parameter η for a rotating body is ≤10(-11) with a four-order improvement over previous results. The anomalous torque per unit angular momentum parameter λ is constrained to (-0.05±3.67)×10(-15) s(-1), (0.24±0.98)×10(-15) s(-1), and (0±3.6)×10(-13) s(-1), respectively, in the directions of geodetic effect, frame-dragging effect, and angular momentum axis; the dimensionless frequency-dependence parameter κ is constrained to (1.75±4.96)×10(-17), (1.80±1.34)×10(-17), and (0±3)×10(-14), respectively.     

Measurement of the forward-backward asymmetry in the B→K*μ(+)μ(-) decay and first observation of the B(s)0→ϕμ(+)μ(-) decay

We reconstruct the rare decays B(+)→K(+)μ(+0μ(-0, B90)→K*(892)(0)μ(+)μ(-), and B(s)(0)→?(1020)μ(+)μ(-) in a data sample corresponding to 4.4 fb(-1) collected in pp collisions at √[s]=1.96 TeV by the CDF II detector at the Tevatron Collider. Using 121±16 B(+)→K(+)μ(+)μ(-) and 101±12 B(0)→K(*0)μ(+)μ(-) decays we report the branching ratios. In addition, we report the differential branching ratio and the muon forward-backward asymmetry in the B(+) and B(0) decay modes, and the K(*0) longitudinal polarization fraction in the B(0) decay mode with respect to the squared dimuon mass. These are consistent with the predictions, and most recent determinations from other experiments and of comparable accuracy. We also report the first observation of the B(s)(0)→?μ(+)μ(-) decay and measure its branching ratio BR(B(s)(0)→?μ(+)μ(-))=[1.44±0.33±0.46]×10(-6) using 27±6 signal events. This is currently the most rare B(s)(0) decay observed.