Probing new physics through B→Kl + l − decays in R-parity violating minimal supersymmetric standard model

We study the decay rate of the process B→Kl ⁺ l ^? (l=e,μ) and some of its other related observables, like the forward–backward asymmetry (A _FB), polarization asymmetry (PA), double branching ratio and CP asymmetry (A _CP) in the R-parity violating Minimal Supersymmetric Standard Model ( $\not \!{R}_{p}$ MSSM). We have performed an error analysis of the differential branching fraction, A _FB and CP asymmetry. The analysis shows that theoretical results based on $\not \!{R}_{p}$ MSSM as an additional effect are compatible with the standard model. A _FB is found to be zero, in agreement with SM. The average A _CP is not only found to be significant in comparison with SM, but it is also compatible with the measured value within errors.     

Status of the NPDGamma Experiment at the SNS

The main goal of the NPDGamma experiment is to measure the gamma-ray asymmetry with respect to the neutron spin direction in the nuclear reaction $\overrightarrow{n}+ p \rightarrow d + \gamma$ . The up-down asymmetry A _γ has a predicted size of the order of 5 ·10^???8 , and the NPDGamma experiment is designed to measure it with an uncertainty of about 10^???8. To test the entire apparatus the gamma-ray asymmetry from neutron capture was measured using a Cl target followed by measurements on Al to establish the relevant background levels. At present the experiment is taking data with a liquid H ₂ target to measure the parity violation on the $\overrightarrow{n} + p \rightarrow d + \gamma$  reaction and extract the ΔI?=?1 part of the hadronic weak interaction.     

Effects of new neutral currents at linear electron-positron colliders

Effects that are induced by contact four-fermion interactions in the processes e ⁺ e ^? → μ ⁺ μ ^?, $\bar bb$ , and $\bar cc$ at $\sqrt s = 0.5$ TeV linear electron-positron colliders are investigated for the case of longitudinally polarized initial beams. This analysis employs new integrated observables constructed from the polarized cross sections for the scattering of final fermions into the forward (σ _F) and the backward (σ _B) hemisphere in such a way that they single out the helicity cross sections for the processes in question. This property of the observables makes it possible to perform, in the most general form, a model-independent analysis of contact four-fermion interactions and to set constraints on their parameters. It is also shown that the sensitivity of new polarization observables to contact interactions is noticeably higher than the corresponding sensitivity of canonical observables like σ, A _FB, A _LR, and A _LR,FB.     

Neutrino production of same-sign dimuons at the Fermilab Tevatron

The rate of neutrino- and antineutrino-induced prompt same-sign dimuon production in steel was measured using a sample of μ^?μ^? events and 25 μ⁺μ⁺ events withP _μ>9 GeV/c, produced in 1.5 millionv _μ and 0.3 million \(\overline {v_\mu }\) induced charged-current events with energies between 30 GeV and 600 GeV. The data were obtained with the Chicago-Columbia-Fermilab-Rochester (CCFR) neutrino detector in the Fermilab Tevatron Quadrupole Triplet Neutrino Beam during experiments E 744 and E 770. After background subtraction, the prompt rate of same-sign dimuon production is (0.53±0.24)×10^?4 perv _μ charged-current event and (0.52±0.33)×10^?4 per \(\overline {v_\mu }\) charged-current event. The kinematic distributions of the same-sign dimuon events after background subtraction are consistent with those of the non-prompt background due to meson decays in the hadron shower of a charged-current event. Calculations ofc \(\bar c\) gluon bremsstrahlung, based on improved measurements of the charm mass parameter and nucleon structure functions by the CCFR collaboration, yield a prompt rate of (0.09±0.39)×10^?4 perv _μ charged-current event. In this case,c \(\bar c\) gluon bremsstrahlung is probably not an observable source of prompt same-sign dimuons.     

Measurement of the forward-backward asymmetry of μ+μ− pairs in CMS

The measurement of the forward-backward asymmetry A _FB and the effective weak mixing angle with the Drell-Yan process at the LHC is presented. The samples of 2011 collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of 5 fb^?1 and 1.1 fb^?1, were used. The results are consistent with the standard model expectations.     

A simple event weighting technique: optimizing the measurement of the forward-backward asymmetry of Drell-Yan dilepton and top-antitop pairs at hadron colliders

We describe a simple technique for optimizing the extraction of the forward-backward asymmetry (A _fb) of Drell-Yan lepton pairs (e ⁺ e ^?, μ ⁺ μ ^?) produced in $\bar{p}p$ and pp collisions at hadron colliders. The method employs simple event weights which are functions of the rapidity and |cos?θ| decay angle of the lepton pair. It yields the best estimate of the acceptance corrected parton level ( $\bar{q}q$ ) forward backward asymmetry as a function of final state dilepton mass (M _{? ?} ). Typically, when compared to the simple count method, the technique reduces the statistical errors by 20% for $\bar{p}p$ , and 40% for pp collisions, respectively. The method is equivalent to using the maximum likelihood method, but is much easier to implement. The technique can be used to search for new high mass and large width Z’ bosons which may be best detected through the observation of deviations from the Standard Model expectation for the forward-backward asymmetry. The technique can also be applied in the extraction of the foward-backward asymmetry in the production of top-antitop pairs.     

MC-Simulation of the Transverse Double Spin Asymmetry for RHIC

We give a leading order estimate of the hadronic transverse double spin asymmetry in the Drell-Yan process at RHIC using Sphinx tt,anew polarized version ofthe Monte Carlo Pythia 5.6. We also calculate the statistical error to next to leading order with Pythia 5.7. Both quantities are of the same order if one assumes that the transversity weighted parton distributions equal the helicity weighted ones at some low perturbative scale Q ₀ ² .     

Physics beyond the Standard Model through b → s μ ?+? μ ? transition

A comprehensive study of the impact of new-physics operators with different Lorentz structures on decays involving the b ?? s ?? ^?+? ?? ^? transition is performed. The effects of new vector?Caxial vector (VA), scalar?Cpseudoscalar (SP) and tensor (T) interactions on the differential branching ratios, forward?Cbackward asymmetries (A _FB??s), and direct CP asymmetries of ${\bar B}_{\rm s}^0 \to \mu^+ \mu^-$ , ${\bar B}_{\rm d}^0 \to$ $ X_{\rm s} \mu^+ \mu^-$ , ${\bar B}_{\rm s}^0 \to \mu^+ \mu^- \gamma$ , ${\bar B}_{\rm d}^0 \to {\bar K} \mu^+ \mu^-$ , and ${\bar B}_{\rm d}^0\to {\bar{K}^*} \mu^+ \mu^-$ are examined. In ${\bar B}_{\rm d}^0\to {\bar{K}^*} \mu^+ \mu^-$ , we also explore the longitudinal polarization fraction f _L and the angular asymmetries $A_{\rm T}^{(2)}$ and A _LT, the direct CP asymmetries in them, as well as the triple-product CP asymmetries $A_{\rm T}^{\rm (im)}$ and $A^{\rm (im)}_{\rm LT}$ . While the new VA operators can significantly enhance most of the observables beyond the Standard Model predictions, the SP and T operators can do this only for A _FB in ${\bar B}_{\rm d}^0 \to {\bar K} \mu^+ \mu^-$ .     

Spin Effects in the Interaction of Antiprotons with the Deuteron at Low and Intermediate Energies

Antiproton-deuteron scattering is analyzed within the Glauber theory, accounting for the full spin dependence of the underlying \({\bar{N}N}\) amplitudes. The latter are taken from the Jülich \({\bar{N}N}\) models and from a recently published new partial-wave analysis of \({\bar{p}p}\) scattering data. Predictions for differential cross sections and the spin observables \({A_y^d}\) , \({A_y^{\bar{p}}}\) , A _xx , A _yy are presented for antiproton beam energies up to about 300 MeV. The efficiency of the polarization buildup for antiprotons in a storage ring is investigated.     

Extracting angular correlations from the rare decay \bar Bd \to \bar K*^0 μ + μ − at LHCb

$ \bar Bd \to \bar K*^0 $ μ ⁺ μ ^? is a rare flavor-changing neutral-current decay. It proceeds via a b → s quark transition and is sensitive to many classes of new physics model. In this article the theoretical framework relevant to making a measurement at LHCb, the precision flavor experiment at the Large Hadron Collider, will be introduced. Progress made towards using a full angular analysis to extract A _FB, the forward-backward asymmetry of the μ pair, will be covered and its implications for the precision of the A _FB zero-crossing-point measurement discussed.     

Mixings and CP violations of theB^0 - \bar B^0 system in the four-generation model

We study the mixings and CP violations in the \(B^0 - \bar B^0 \) system together with the \(K^0 - \bar K^0 \) one in the four-generation model, taking into account the ARGUS data for the \(B_d^0 - \bar B_d^0 \) mixing. We take typical six cases of the mixing hierarchy and search for the allowed regions of three phases in the 4×4KM matrix. The CP violating parameter ? _K in the \(K^0 - \bar K^0 \) system gives a severe constraint for the phases, and the smaller mixing than that in the three-generation model is predicted for the \(B_s^0 - \bar B_s^0 \) system. The asymmetry parameters for the two-body non-leptonic decays of theB ⁰ and \(\bar B^0 \) mesons are also predicted.     

Pulse ENDOR studies on the radical pair P 700 +· A 1 ·− and the photoaccumulated quinone acceptor A 1 ·− of photosystem I

The secondary acceptor A₁ of the electron transport chain(s) of photosystem (PS) I is a phylloquinone (vitamin K₁, VK₁). Pulse electron paramagnetic resonance and electron nuclear double resonance (ENDOR) experiments at X-band frequencies were performed on the photoaccumulated acceptor radical A ₁ ^·? and the radical pair state P ₇₀₀ ^·+ A ₁ ^·? in PS I ofThermosynechococcus elongatus. The data obtained were compared with data from the respective radical anion of VK₁ in organic solvents. The unusualg tensor magnitude of A ₁ ^·? is explained by the hydrophobic binding pocket of this radical. The hyperfine couplings and the spin (and charge) density distribution is very different for A ₁ ^.? in PS I and VK ₁ ^·? in frozen alcoholic solution. This is attributed to a rather strong one-sided hydrogen bond to A ₁ ^·? . The presence of a hydrogen bond to A ₁ ^·? has only a minor effect ong. The hyperfine coupling constants of A ₁ ^·? determined from the radical pair spectra deviate only slightly from those derived from photoaccumulated A ₁ ^·? in PS I treated with dithionite at high pH. ENDOR resonances of the proton in a H bond were detected and an estimate of the strength and geometry of this bond to A ₁ ^·? was obtained. The significance of the hydrogen bond and other (hydrophobic) interactions of A₁ with the surrounding are briefly discussed.     

Leading/nonleading charm-production asymmetry in Σ− p interactions

The asymmetry between the spectra of leading and nonleading charmed mesons that was measured in Σ^? A interactions at p _L=340 GeV/c in the WA89 experiment is described within the Model of Quark-Gluon Strings (QGS model also known as QGSM) under the assumption that there is a fraction of charmed sea quark-antiquark pairs (intrinsic charm) in an interacting hyperon. It is shown that the asymmetries between D ^?-and D ⁺-meson spectra and between D _s ^? -and D _s ⁺ -meson spectra can be approximated by QGSM curves obtained with the same string-fragmentation parameter, a ₁=10, and the same intrinsic-charm fraction, $\delta _{c,\bar c} = 0.01$ , as those that were used in describing D _s ^? /D _s ⁺ -meson asymmetry of π^? A experiments in previous studies. The asymmetry between the spectra of Λ_c and $\bar \Lambda _c $ that was measured in Σ^? A collisions at p _L=600 GeV/c in the E781 experiment is also described within this scheme. The QGSM results are compared with the results of the calculations in the next-to-leading approximation of perturbative QCD that were performed by other authors.     

Asymmetry extraction in experiment for measurement of neutron electric form-factor at high momentum transfer

Measurement of the neutron electric form-factor G _E ⁿ for the values of the transferred momentum Q ² = 1.3, 1.7, 2.5, and 3.5 (GeV/c)² has been performed at the Jefferson Laboratory (USA). The experiment used the technique of double polarization where the asymmetry of the quasielastic scattering in the semi-inclusive ³ $ \overrightarrow {He} $ ( $ \vec e $ . e′n)pp reaction is measured. The obtained asymmetry is connected directly with the ratio of electric to magnetic form-factors of the neutron which allows obtaining the former with use of the known values of the latter. This work presents the technique of extraction of the asymmetry from the obtained experimental data.     

Search for massive photon pair production at the CERN intersecting storage rings

A search for massive photon pair production at \(\sqrt s = 63 GeV\) has been carried out on the data sample previously employed for the electron pair production study. Positive evidence is reported form _γγ>6GeV, with a production cross-section similar to Drell-Yan electron pairs. The ratio γγ/π⁰π⁰ was measured to be ～10^?3 for ap _T of each γ or γ or π⁰ above 3 GeV/c.     

Mass mixing,CP violation and left-right symmetry for heavy neutral mesons

We investigate \(M^0 - \bar M^0 \) mixing and CP violation in the minimal left-right symmetric gauge model with spontaneous P and CP violation. The dominant contributions to the mixing amplitude including QCD corrections are calculated explicitly for \(B^0 - \bar B^0 \) . While the amount of mixing is not much changed with respect to the standard model leftright symmetry can give rise to significantly larger CP violation in the \(B_s^0 - \bar B_s^0 \) system (up to two orders of magnitude for the dilepton charge asymmetry). Sizable CP violating effects require that the left-right contribution to theK _L K _S mass difference has the same sign as the standard model contribution. We also comment on \(D^0 - \bar D^0 \) mixing including a careful discussion of the standard model prediction for the short distance part.     

On the possibility of observation of a 0-f 0 mixing in the pn → da 0 reaction

It is shown that, if isospin is not conserved in a ₀ ⁰ -and f ₀-meson mixing, forward-backward asymmetry arises in the pn→da ₀ ⁰ reaction. This effect increases near the reaction threshold. The asymmetry is estimated within the framework of a model in which the a ₀ ⁰ -f ₀ mixing is due to the virtual π⁰?η transition and the difference in masses of the charged and neutral kaons in decay channels. The angular asymmetry near the threshold of the pn→da ₀ ⁰ reaction was found to be large, of the order of 8–15%.     

Leading-particle effects in the spectra of Λc and \bar \Lambda _c produced in Σ− p, pp, and π − p interactions

The spectra of leading and nonleading charmed baryons (Λ_c and $\bar \Lambda _c$ ) and the asymmetries between these spectra measured in Σ^? A, π ^? A, and pA collisions at p _L =600 GeV/c in the E781 experiment are simultaneously described within the framework of the Quark-Gluon String Model (QGSM). It is shown that the charmed baryon spectra can be fitted by QGSM curves calculated with the parameter of diquark fragmentation, $a_f^{\Lambda _c } = 0.006$ . It was found in this experiment that the asymmetry between the spectra of Λ_c and $\bar \Lambda _c$ in π ^? A collisions is of nonzero value. It might be described in our model only assuming that the string junction is transferred from target proton into the kinematical region of pion projectile fragmentation.     

Neutrino-induced deuteron disintegration in an experiment at the Krasnoyarsk nuclear reactor

The results of studying antineutrino interactions with deuterons (CCD and NCD reactions) and hydrogen (CCP) at the Krasnoyarsk underground reactor with the Deuteron detector are presented. The cross sections for NCD and CCD were measured with a precision of 9%. For CCP, the precision is 3%: σ _expt ^NCD =(3.35±0.31)×10^?44 cm²/fission ²³⁵U, σ _expt ^NCD =(1.08±0.09)×10^?44 cm²/fission ²³⁵U, and σ _expt ^NCD =(6.39±0.19)×10^?43 cm²/fission ²³⁵U. The precision of the experimental results is close to the theoretical one and is in good agreement with other experiments. The limit on the parameters of antineutrino oscillations into the sterile state was obtained: Δm ²≤4.7×10^?2 eV² for sin²(2?)=1.0 (68% C.L.). A comparison of the measured and theoretical cross section gives us the neutron-neutron scattering length of a _nn(S)=?17±6 fm in the approach of zero momentum transfers. The weak neutral current constant is in good agreement with the prediction of the Standard Model: G _A ^NC =G _A ^CC /0.932±0.056.     

Resonance studies at STAR

Preliminary results from measurements of resonances (K ^*0(892), $\overline {K*^0 } (892)$ , Φ(1020), and ρ(770)) and weakly decaying particles (Λ(1116), $\bar \Lambda (1116)$ , and K _S ⁰ (498)) are presented. The measurements are performed at mid-rapidity by the STAR detector in $\sqrt {s_{NN} } = 130$ GeV Au?Au collisions at RHIC. The ratios K ^*0/h?, $\overline {K*^0 } /K$ , and $\bar \Lambda /\Lambda $ are compared to measurements at different energies and colliding systems. Estimates of thermal parameters, such as temperature and baryon chemical potential, are also presented.