Nuclear spin structure measurements at SLAC

title: Quark-parton models and the neutron charge radius

title: CEBAF — a high energy, high duty factor electron accelerator for nuclear physics☆
abstract: The Nuclear Science Advisory Committee has recommended the construction of the Continuous Electron Beam Accelerator Facility (CEBAF) as proposed by the Southeastern Universities Research Association (SURA), a consortium of more than thirty institutions in the southeastern United States. The accelerator will be capable of delivering intense (Iave > 100 μA), quasi-continuous (duty Factor > 90%) beams of electrons with energies up to 4.8 GeV. Short (1.2 μs), intense (Ipk = 200 mA) pulses of electrons will be accelerated by passing twice through a conventional pulsed linac. The pulses then will be injected into and stored in a pulse stretcher ring, the circumference of which is close to the length of the electron pulse. During the period between pulses (1ms) the stored electrons will be extracted to yield a high duty factor beam. Delivery of arbitrarily polarized beams will be possible. Experimental facilities will include three end stations. Two will be used for experiments utilizing the primary electron beam; the third will serve as a tagged photon facility.

title: Off-shell effects in quasielastic electron nucleus scattering
abstract: Using the Ward-Takahashi identity, on-shell condition, bound Dirac equation and off-shell expansion, a reduced version of half off-shell virtual photon nucleon vertex has been suggested. The vertex are decomposed into several different order terms: the on-shell terms, first and second off-shell terms. The off-shell behaviour of the form factors is discussed in the one meson loop model. Using the reduced vertex and parametrized off-shell form factors the quasielastic response functions are calculated for several nuclei at ¦q¦–kf and for56Fe at large ¦q¦ up to 1.14 GeV/c and at −q2=0.9 (GeV/c)2. The Coulomb sums are evaluated and a comparison of the theoretical prediction with data is given. The off-shell electron nucleon cross section is calculated and compared with the “cc1” off-shell extrapolation.

title: Pion-helium scattering above the (3,3) resonance
abstract: Differential cross sections are reported for ..pi../sup +/+/sup 3,4/He elastic scattering at 260, 295, and 310 MeV and ..pi../sup -/+/sup 3,4/He at 295 MeV. The angular distributions )except for ..pi../sup -/+/sup 3/He) confirm the fixed angle (thetaapprox. =75/sup 0/) minimum seen at lower energies (caused by the (3,3) ..pi..+N resonance dominance) and show a deep minimum at thetaapprox. =110/sup 0/. Comparisons are made to ..pi..+d and the current discussion of pion excitation of intermediate dibaryon and ..delta..N states.

title: Computer Modeling of Internal Targets in Electron Storage Rings
abstract: The effect of thin (1-50 ¿gm/cm2) internal targets on beam quality in electron storage rings is evaluated. The internal target is modeled assuming that scattering is the result of elastic collisions between the beam electrons and the target nuclei. A screened coulomb potential is used and single and plural scattering mechanisms are included. A storage ring particle tracking code, DIMAT, was modified to include the internal target model and used to obtain the results discussed. Beam particle loss distributions and beam envelope "growth times" are given and discussed in light of damping mechanisms inherent in electron storage ring designs.

title: Branching fraction and CP asymmetry of the decays $B^+ \to K_{\rm \scriptscriptstyle S}^0 \pi^+$ and $B^+ \to K_{\rm \scriptscriptstyle S}^0 K^+$
abstract: An analysis of B+ → K0 Sπ and B+ → K0 SK decays is performed with the LHCb experiment. The pp collision data used correspond to integrated luminosities of 1 fb−1 and 2 fb−1 collected at centre-of-mass energies of √ s = 7 TeV and √ s = 8 TeV, respectively. The ratio of branching fractions and the direct CP asymmetries are measured to be B(B+ → K0 SK)/B(B → K0 Sπ) = 0.064 ± 0.009 (stat.) ± 0.004 (syst.), ACP (B+ → K0 Sπ) = −0.022 ± 0.025 (stat.) ± 0.010 (syst.) and ACP (B+ → K0 SK) = −0.21± 0.14 (stat.)± 0.01 (syst.). The data sample taken at √ s = 7 TeV is used to search for B+ c → K0 SK decays and results in the upper limit (fc · B(B+ c → K0 SK))/(fu · B(B+ → K0 Sπ)) < 5.8× 10−2 at 90% confidence level, where fc and fu denote the hadronisation fractions of a b̄ quark into a B + c or a B + meson, respectively.  8. 12 77 v2 [ he pex ] 1 N ov 2 01 3

title: Observation of the resonant character of the Z(4430)(-) state.
abstract: Resonant structures in B^{0}→ψ^{'}π^{-}K^{+} decays are analyzed by performing a four-dimensional fit of the decay amplitude, using pp collision data corresponding to 3  fb^{-1} collected with the LHCb detector. The data cannot be described with K^{+}π^{-} resonances alone, which is confirmed with a model-independent approach. A highly significant Z(4430)^{-}→ψ^{'}π^{-} component is required, thus confirming the existence of this state. The observed evolution of the Z(4430)^{-} amplitude with the ψ^{'}π^{-} mass establishes the resonant nature of this particle. The mass and width measurements are substantially improved. The spin parity is determined unambiguously to be 1^{+}.

title: Some aspects of free field resolutions in 2-D CFT with application to the quantum Drinfeld-Sokolov reduction
abstract: We review some aspects of the free field approach to two-dimensional conformal field theories. Specifically, we discuss the construction of free field resolutions for the integrable highest weight modules of untwisted affine Kac-Moody algebras, and extend the construction to a certain class of admissible highest weight modules. Using these, we construct resolutions of the completely degenerate highest weight modules of W-algebras by means of the quantum Drinfeld-Sokolov reduction. As a corollary we derive character formulae for these degenerate highest weight modules.

title: BV Structure of the Cohomology of Nilpotent Subalgebras and the Geometry of(W) Strings
abstract: AbstractGiven a simple, simply laced, complex Lie algebra 
$$\mathfrak{g}$$
corresponding to the Lie group G, let 
$$\mathfrak{n}_ + $$
 be thesubalgebra generated by the positive roots. In this Letter we construct aBV algebra 
$${\text{BV}}[\mathfrak{g}]$$
 whose underlying graded commutative algebra is given by the cohomology, with respect to 
$$\mathfrak{n}_ + $$
, of the algebra of regular functions on G with values in 
$$ \wedge (\mathfrak{n}_ + \backslash \mathfrak{g})$$
. We conjecture that 
$${\text{BV}}[\mathfrak{g}]$$
 describes the algebra of allphysical (i.e., BRST invariant) operators of the noncritical 
$$\mathcal{W}[\mathfrak{g}]$$
string. The conjecture is verified in the two explicitly known cases,
$$\mathfrak{g} = \mathfrak{s}\mathfrak{l}$$
2 (the Virasoro string) and 
$$\mathfrak{g} = \mathfrak{s}\mathfrak{l}$$
3 (the 
$$\mathcal{W}_3 $$
 string).

title: Observation of a resonance in $B^+ \to K^+ \mu^+\mu^-$ decays at low recoil
abstract: A broad peaking structure is observed in the dimuon spectrum of $B^+ \to K^+ \mu^+\mu^-$ decays in the kinematic region where the kaon has a low recoil against the dimuon system. The structure is consistent with interference between the $B^+ \to K^+ \mu^+\mu^-$ decay and a resonance and has a statistical significance exceeding six standard deviations. The mean and width of the resonance are measured to be $4191^{+9}_{-8}\mathrm{\,Me\kern -0.1em V/}c^2$ and $65^{+22}_{-16}\mathrm{\,Me\kern -0.1em V/}c^2$, respectively, where the uncertainties include statistical and systematic contributions. These measurements are compatible with the properties of the $\psi(4160)$ meson. First observations of both the decay $B^+ \to \psi(4160) K^+$ and the subsequent decay $\psi(4160) \to \mu^+\mu^-$ are reported. The resonant decay and the interference contribution make up 20\,% of the yield in the low recoil region, which is larger than theoretical estimates.