The production ofb andc quarks ine+e− annihilation has been studied with the CELLO detector in the range from 35 GeV up to the highest PETRA energies. The heavy quarks have been tagged by their semileptonic decays. The charge asymmetries forb quarks at 35 and 43 GeV have been found to beAb=−(22.2±8.1)% andAb=−(49.1±16.5)%, respectively, using a method incorporating jet variables and their correlations for the separation of the heavy quarks from the back ground of the lighter quarks. Forc quarks we obtainAc=−(12.9±8.8)% andAc=+(7.7±14.0)%, respectively. The axial vector coupling constants of the heavy quarksc andb are found to beac=+(0.29±0.46) andab=−(1.15±0.41) taking\(B^0 \overline {B^0 } \) mixing into account. The results are in agreement with the expectations from the standard model.
BOTTOM quark charge asymmetry.
CHARMED quark charge asymmetry.
The forward-backward asymmetries of$$e^ + e^ - \to Z^0 \to b\bar b and e^ + e^ - \to Z^0 \to c\bar c$$
Measurement of the asymmetry in b-quark production on the Z0 peak using a two parameter fit, neglecting the effects of B0-BBAR0 mixing.
Measurement of the asymmetry in b-quark production on the Z0 peak using a two parameter fit and correcting for B0-BBAR0 mixing. The second systematic error is due to the uncertainty of the mixing factor.
Measurement of the asymmetry in c-quark production on the Z0 peak using a two parameter fit.
The COMPASS Collaboration at CERN has measured the transverse spin azimuthal asymmetry of charged hadrons produced in semi-inclusive deep inelastic scattering using a 160 GeV positive muon beam and a transversely polarised NH_3 target. The Sivers asymmetry of the proton has been extracted in the Bjorken x range 0.003<x<0.7. The new measurements have small statistical and systematic uncertainties of a few percent and confirm with considerably better accuracy the previous COMPASS measurement. The Sivers asymmetry is found to be compatible with zero for negative hadrons and positive for positive hadrons, a clear indication of a spin-orbit coupling of quarks in a transversely polarised proton. As compared to measurements at lower energy, a smaller Sivers asymmetry for positive hadrons is found in the region x > 0.03. The asymmetry is different from zero and positive also in the low x region, where sea-quarks dominate. The kinematic dependence of the asymmetry has also been investigated and results are given for various intervals of hadron and virtual photon fractional energy. In contrast to the case of the Collins asymmetry, the results on the Sivers asymmetry suggest a strong dependence on the four-momentum transfer to the nucleon, in agreement with the most recent calculations.
The Sivers asymmetry, from the 2010 data set, for positive hadrons as a function of X for full range. Also shown are the mean values of other variables plus the correlation with the Collins data measurments.
The Sivers asymmetry, from the 2010 data set, for negative hadrons as a function of X for full range. Also shown are the mean values of other variables plus the correlation with the Collins data measurments.
The Sivers asymmetry, from the 2010 data set, for positive hadrons as a function of PT for full range. Also shown are the mean values of other variables plus the correlation with the Collins data measurments.
The COMPASS Collaboration at CERN has measured the transverse spin azimuthal asymmetry of charged hadrons produced in semi-inclusive deep inelastic scattering using a 160 GeV positive muon beam and a transversely polarised NH_3 target. The Collins asymmetry of the proton was extracted in the Bjorken x range 0.003<x<0.7. These new measurements confirm with higher accuracy previous measurements from the COMPASS and HERMES collaborations, which exhibit a definite effect in the valence quark region. The asymmetries for negative and positive hadrons are similar in magnitude and opposite in sign. They are compatible with model calculations in which the u-quark transversity is opposite in sign and somewhat larger than the d-quark transversity distribution function. The asymmetry is extracted as a function of Bjorken $x$, the relative hadron energy $z$ and the hadron transverse momentum p_T^h. The high statistics and quality of the data also allow for more detailed investigations of the dependence on the kinematic variables. These studies confirm the leading-twist nature of the Collins asymmetry.
The Collins asymmetry, from the 2010 data set, for positive hadrons as a function of X for full range. Also shown are the mean values of other variables plus the correlation with the Sivers data measurments.
The Collins asymmetry, from the 2010 data set, for negative hadrons as a function of X for full range. Also shown are the mean values of other variables plus the correlation with the Sivers data measurments.
The Collins asymmetry, from the 2010 data set, for positive hadrons as a function of PT for full range. Also shown are the mean values of other variables plus the correlation with the Sivers data measurments.
The differential cross sections \sigma_0=\sigma_T+\epsilon \sigma_L, \sigma_{LT}, and \sigma_{TT} of \pi^0 electroproduction from the proton were measured from threshold up to an additional center of mass energy of 40 MeV, at a value of the photon four-momentum transfer of Q^2= 0.05 GeV^2/c^2 and a center of mass angle of \theta=90^\circ. By an additional out-of-plane measurement with polarized electrons \sigma_{LT'} was determined. This showed for the first time the cusp effect above the \pi^+ threshold in the imaginary part of the s-wave. The predictions of Heavy Baryon Chiral Perturbation Theory are in disagreement with these data. On the other hand, the data are somewhat better predicted by the MAID phenomenological model and are in good agreement with the dynamical model DMT.
Beam helicity asymmetry.
We present a measurement of asymmetries in the production of $\Lambda_c^+$ and $\Lambda_c^-$ baryons in 500 GeV/c $\pi^-$--nucleon interactions from the E791 experiment at Fermilab. The asymmetries were measured as functions of Feynman x ($x_F$) and transverse momentum squared ($p_T^2$) using a sample of $1819 \pm 62$ $\Lambda_c$'s observed in the decay channel $\Lambda_c \to pK^-\pi^+$. We observe more $\Lambda_c^+$ than $\Lambda_c^-$ baryons, with an asymmetry of $(12.7\pm3.4\pm1.3) %$ independent of $x_F$ and $p_T^2$ in our kinematical range $(-0.1 < x_F < 0.6$ and $0.0 < p_T^2 < 8.0 (GeV/c)^2$). This $\Lambda_c$ asymmetry measurement is the first with data in both the positive and negative $x_F$ regions.
No description provided.
No description provided.
We report the first measurement of the lepton forward-backward asymmetry ${\cal A}_{\rm FB}$ as a function of the squared four-momentum of the dilepton system, $q^2$, for the electroweak penguin process $B \rightarrow X_s \ell^+ \ell^-$ with a sum of exclusive final states, where $\ell$ is an electron or a muon and $X_s$ is a hadronic recoil system with an $s$ quark. The results are based on a data sample containing $772\times10^6$ $B\bar{B}$ pairs recorded at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB $e^+ e^-$ collider. ${\cal A}_{\rm FB}$ for the inclusive $B \rightarrow X_s \ell^+ \ell^-$ is extrapolated from the sum of 10 exclusive $X_s$ states whose invariant mass is less than 2 GeV/$c^2$. For $q^2 > 10.2$ GeV$^2$/$c^2$, ${\cal A}_{\rm FB} < 0$ is excluded at the 2.3$\sigma$ level, where $\sigma$ is the standard deviation. For $q^2 < 4.3$ GeV$^2$/$c^2$, the result is within 1.8$\sigma$ of the Standard Model theoretical expectation.
The value of ASYM(FB) obtained from the fit in each of the four Q**2 bins.
Spin asymmetries for the 16O(γ→,pπ−) reaction are reported for incident photon energies of 293 ± 20 MeV, proton angles ranging from 28° to 140° (lab), and pion angles of 35° to 115°. The data are compared with calculations in a quasifree plane-wave impulse approximation model. This model is in good agreement with the data at small momentum transfer q, but does not follow the trend of the data at large q. Sensitivity to the Δ-nucleus potential and to modification of the Δ lifetime from nuclear medium effects are explored using a simple modification of the Δ propagator in the calculations.
The data are extracted from the figures by S.Slabospitsky. ASYM is the spin asymmetry. It is the ratio of the difference to the sum of the cross sections with the photon's linear polarization oriented parallel or perpendicular to the scattering plane.
The data are extracted from the figures by S.Slabospitsky. ASYM is the spin asymmetry. It is the ratio of the difference to the sum of the cross sections with the photon's linear polarization oriented parallel or perpendicular to the scattering plane.
The data are extracted from the figures by S.Slabospitsky. ASYM is the spin asymmetry. It is the ratio of the difference to the sum of the cross sections with the photon's linear polarization oriented parallel or perpendicular to the scattering plane.
The parity-violating asymmetries between a longitudinally-polarized electron beam and an unpolarized deuterium target have been measured recently. The measurement covered two kinematic points in the deep inelastic scattering region and five in the nucleon resonance region. We provide here details of the experimental setup, data analysis, and results on all asymmetry measurements including parity-violating electron asymmetries and those of inclusive pion production and beam-normal asymmetries. The parity-violating deep-inelastic asymmetries were used to extract the electron-quark weak effective couplings, and the resonance asymmetries provided the first evidence for quark-hadron duality in electroweak observables. These electron asymmetries and their interpretation were published earlier, but are presented here in more detail.
Asymmetry results on $\vec e-^2$H parity-violating scattering from the PVDIS experiment at JLab.
Asymmetry results on $\vec e-^2$H parity-violating scattering from the PVDIS experiment at JLab, for RES I settings.
Asymmetry results on $\vec e-^2$H parity-violating scattering from the PVDIS experiment at JLab, for RES II settings.
We present a measurement of the azimuthal asymmetries of two charged pions in the inclusive process $e^+e^-\rightarrow \pi\pi X$ based on a data set of 62 $\rm{pb}^{-1}$ at the center-of-mass energy $\sqrt{s}=3.65$ GeV collected with the BESIII detector. These asymmetries can be attributed to the Collins fragmentation function. We observe a nonzero asymmetry, which increases with increasing pion momentum. As our energy scale is close to that of the existing semi-inclusive deep inelastic scattering experimental data, the measured asymmetries are important inputs for the global analysis of extracting the quark transversity distribution inside the nucleon and are valuable to explore the energy evolution of the spin-dependent fragmentation function.
Results of $A_{\rm UL}$ and $A_{\rm UC}$ in each ($z_{1},z_{2}$) and $p_{t}$ bin. The averages $\langle z_i\rangle$, $\langle p_t\rangle$ and $\rm \frac{\langle sin^2\theta_{2}\rangle }{\rm \langle 1+cos^2\theta_{2} \rangle }$ are also given.
Results of $A_{\rm UL}$ and $A_{\rm UC}$ in each ($z_{1},z_{2}$) and $p_{t}$ bin. The averages $\langle z_i\rangle$, $\langle p_t\rangle$ and $\rm \frac{\langle sin^2\theta_{2}\rangle }{\rm \langle 1+cos^2\theta_{2} \rangle }$ are also given.
We report measurements of the asymmetry A_parallel for inclusive hadron production on longitudinally polarized proton and deuteron targets by circularly polarized photons. The photons were produced via internal and external bremsstrahlung from an electron beam of 48.35 GeV. Asymmetries for both positive and negative signed hadrons, and a subset of identified pions, were measured in the momentum range 10<P<30 GeV at 2.75 and 5.5 degrees. Small non-zero asymmetries are observed for the proton, while the deuteron results are consistent with zero. Recent calculations do not describe the data well.
The asymmetry for polarized photoproduction of inclusive hadrons from a polarized proton target. The errors are statistical only.
The asymmetry for polarized photoproduction of inclusive identified pions from a polarized proton target. The errors are statistical only.
The asymmetry for polarized photoproduction of inclusive hadrons from a polarized deuteron target. The errors are statistical only.
At the tagged photon facility PHOENICS at the Bonn accelerator ELSA a measurement of the target asymmetry of the reaction γp→pη from threshold to 1150 MeV has been performed. Simultaneously the reaction γp→pπ0 has been measured in the first resonance region. Results are presented for both reactions. The target asymmetry data are suited to put considerable constraints on the model parameters used for the theoretical description of meson photoproduction.
The errors include statistical and systematic errors added in quadrature. The target asymmetry determines as the rates belonging to different polarization states: (N_pol-up-N_pol_down)/(N_pol-up+N_pol_down).
The errors include statistical and systematic errors added in quadrature. The target asymmetry determines as the rates belonging to different polarization states: (N_pol-up-N_pol_down)/(N_pol-up+N_pol_down).
The errors include statistical and systematic errors added in quadrature. The target asymmetry determines as the rates belonging to different polarization states: (N_pol-up-N_pol_down)/(N_pol-up+N_pol_down).
Using linearly polarized tagged photons from coherent bremsstrahlung, differential cross sections and beam asymmetries for Compton scattering by 4 He have been measured at MAMI in the energy interval between 150 MeV and 500 MeV for scattering angles of θ γ lab =37°, 93° and 137°, thus largely increasing the available data base. Improved calculations in terms of the Δ -hole model completely fail to describe the data at large scattering angles. The same proved to be true for a schematic model, even after taking into account properties of nuclear photo-absorption in very detail.
Axis error includes +- 0.0/0.0 contribution.
We present a direct measurement of the parity-violation parameter $A_c$ in the coupling of the $Z^0$ to $c$-quarks with the SLD detector. The measurement is based on a sample of 530k hadronic $Z^0$ decays, produced with a mean electron-beam polarization of $|P_e| = 73 %$. The tagging of $c$-quark events is performed using two methods: the exclusive reconstruction of $D^{\ast+}$, $D^+$, and $D^0$ mesons, and the soft-pions ($\pi_s$) produced in the decay of $D^{\ast+}\to D^0 \pi_s^+$. The large background from $D$ mesons produced in $B$ hadron decays is separated efficiently from the signal using precision vertex information. The combination of these two methods yields $A_c = 0.688 \pm 0.041.$
CONST(NAME=A_C) is connected with the forward-backward asymmetry by following way: ASYM(NAME=FB) = ABS(P_e)*CONST(NAME=A_C)*2z/(1 + z**2), where z = cos(theta), theta is the polar angle of the outgoing fermion relative to the incident electron, P_e is the longitudinal polarization of the electron beam. Two values for constant A_c were obtained using two different c-quark tagging methods: exclusive charmed-meson reconstruction (C=EXCLUSIVE) and inclusive soft-pion analysis (C=SOFT_PIONS).
Using data from Fermilab fixed-target experiment E791, we have measured particle-antiparticle production asymmetries for lambda zero, cascade minus, and omega minus hyperons in pi minus-nucleon interactions at 500 GeV/c. The asymmetries are measured as functions of Feynman-x (x_F) and pt^2 over the ranges of -0.12 GE x_F LE 0.12 and 0 GE pt^2 LE 4 (GeV/c)^2. We find substantial asymmetries, even at x_F = 0. We also observe leading-particle- type asymmetries which qualitatively agree with theoretical predictions.
No description provided.
No description provided.
No description provided.
The forward-backward charge asymmetries of theb andc quarks are measured with the JADE detector at PETRA at\(\sqrt s= 35\) GeV and 44 GeV using both electrons and muons to tag the heavy quarks. At\(\sqrt s= 35\) GeV, a simultaneous fit for the two asymmetries yields the resultAb=−9.3±5.2% (state.) ndAc=−9.6±4.0% (stat.). The systematic errors are comparable with the statistical uncertainties. Combining the measurements at both energies and alternately constraining the weak coupling of thec andb quark to their Standard Model values (ac=1,ab=−1) increases the precision of the measurement of coupling constant of the other quark. Using this procedureab=−0.72±0.34 andac=0.79±0.40, where the numbers are corrected for\(B\bar B - mixing\) and the errors include both statistical and systematic contributions. The mixing parameter for continuum\(b\bar b - production\) is determined to be χ-0.24±0.12 if both heavy quark coupling constants are constrained to their values in the Standard Model.
Results of simultaneous fit to both asymmetries. This table is for the CHARMED quark.
Results of simultaneous fit to both asymmetries. This table is for the BOTTOM quark.
Results for BOTTOM quark asymmetry with c asymmetry constrained to the standard model value.
The charmed quark charge asymmetry has been measured at the average centre of mass energy of 35 GeV with the JADE detector at thee+e− storage ring PETRA. Charmed quarks were identified byD*± tagging using the ΔM technique.D*± mesons were reconstructed through their decay intoD0 mesons resulting in (Kπ) π and (K π π π) π final states. The measured charge asymmetryA=−0.149±0.067 is in agreement with the expectation from the electroweak interference effect in quantum flavour dynamics (QFD).
CHARMED quark charge asymmetry.
New high precision measurements of the Collins and Sivers asymmetries of charged hadrons produced in deep-inelastic scattering of muons on a transversely polarised 6LiD target are presented. The data were taken in 2003 and 2004 with the COMPASS spectrometer using the muon beam of the CERN SPS at 160 GeV/c. Both the Collins and Sivers asymmetries turn out to be compatible with zero, within the present statistical errors, which are more than a factor of 2 smaller than those of the published COMPASS results from the 2002 data. The final results from the 2002, 2003 and 2004 runs are compared with naive expectations and with existing model calculations.
Collins asymmetry against PT for all negative hadrons.
Collins asymmetry against Bjorken X for all negative hadrons.
Collins asymmetry against Z for all negative hadrons.
First measurements of the Collins and Sivers asymmetries of charged hadrons produced in deep-inelastic scattering of muons on a transversely polarized 6-LiD target are presented. The data were taken in 2002 with the COMPASS spectrometer using the muon beam of the CERN SPS at 160 GeV/c. The Collins asymmetry turns out to be compatible with zero, as does the measured Sivers asymmetry within the present statistical errors.
Asymmetries as a function of X for LEADING hadrons.
Asymmetries as a function of Z for LEADING hadrons.
Asymmetries as a function of PT for LEADING hadrons.
The measurements of the Collins and Sivers asymmetries of identified hadrons produced in deep-inelastic scattering of 160 GeV/c muons on a transversely polarised 6LiD target at COMPASS are presented. The results for charged pions and charged and neutral kaons correspond to all data available, which were collected from 2002 to 2004. For all final state particles both the Collins and Sivers asymmetries turn out to be small, compatible with zero within the statistical errors, in line with the previously published results for not identified charged hadrons, and with the expected cancellation between the u- and d-quark contributions.
The Collins and Sivers asymmetry as a function of X for 'ALL' positive pions from the 2003-2004 data.. Errors are statistical only.
The Collins and Sivers asymmetry as a function of PT for 'ALL' positive pions from the 2003-2004 data.. Errors are statistical only.
The Collins and Sivers asymmetry as a function of Z for 'ALL' positive pions from the 2003-2004 data.. Errors are statistical only.
Spin-averaged asymmetries in the azimuthal distributions of positive and negative hadrons produced in deep inelastic scattering were measured using the CERN SPS muon beam at $160$ GeV/c and a $^6$LiD target. The amplitudes of the three azimuthal modulations $\cos\phi_h$, $\cos2\phi_h$ and $\sin\phi_h$ were obtained binning the data separately in each of the relevant kinematic variables $x$, $z$ or $p_T^{\,h}$ and binning in a three-dimensional grid of these three variables. The amplitudes of the $\cos \phi_h$ and $\cos 2\phi_h$ modulations show strong kinematic dependencies both for positive and negative hadrons.
ASYMUU(SIN(PHI(HADRON))) asymmetries for positive and negative hadrons as a function of XB. The errors are statistical and systematic.
ASYMUU(SIN(PHI(HADRON))) asymmetries for positive and negative hadrons as a function of Z. The errors are statistical and systematic.
ASYMUU(SIN(PHI(HADRON))) asymmetries for positive and negative hadrons as a function of PT(HADRON). The errors are statistical and systematic.
In 2015, the PHENIX collaboration has measured very forward ($\eta>6.8$) single-spin asymmetries of inclusive neutrons in transversely polarized proton-proton and proton-nucleus collisions at a center of mass energy of 200 GeV. A previous publication from this data set concentrated on the nuclear dependence of such asymmetries. In this measurement the explicit transverse-momentum dependence of inclusive neutron single spin asymmetries for proton-proton collisions is extracted using a bootstrapping-unfolding technique on the transverse momenta. This explicit transverse-momentum dependence will help improve the understanding of the mechanisms that create these asymmetries.
Measured and unfolded forward neutron single spin asymmetries using 3rd order polynomial parameterization in unfolding
Measured and unfolded forward neutron single spin asymmetries using a Power law parameterization in unfolding
Measured and unfolded forward neutron single spin asymmetries using an exponential parameterization in unfolding
Polarized proton-proton collisions provide leading-order access to gluons, presenting an opportunity to constrain gluon spin-momentum correlations within transversely polarized protons and enhance our understanding of the three-dimensional structure of the proton. Midrapidity open-heavy-flavor production at $\sqrt{s}=200$ GeV is dominated by gluon-gluon fusion, providing heightened sensitivity to gluon dynamics relative to other production channels. Transverse single-spin asymmetries of positrons and electrons from heavy-flavor hadron decays are measured at midrapidity using the PHENIX detector at the Relativistic Heavy Ion Collider. These charge-separated measurements are sensitive to gluon correlators that can in principle be related to gluon orbital angular momentum via model calculations. Explicit constraints on gluon correlators are extracted for two separate models, one of which had not been constrained previously.
Data from Figure 1 of open heavy flavor $e^{\pm}$ transverse single-spin asymmetries in transversely polarized p+p collisions as a function of $p_{T}$.
In 2015 the PHENIX collaboration at the Relativistic Heavy Ion Collider recorded $p+p$, $p+$Al, and $p+$Au collision data at center of mass energies of $\sqrt{s_{_{NN}}}=200$ GeV with the proton beam(s) transversely polarized. At very forward rapidities $\eta>6.8$ relative to the polarized proton beam, neutrons were detected either inclusively or in (anti)correlation with detector activity related to hard collisions. The resulting single spin asymmetries, that were previously reported, have now been extracted as a function of the transverse momentum of the neutron as well as its longitudinal momentum fraction $x_F$. The explicit kinematic dependence, combined with the correlation information allows for a closer look at the interplay of different mechanisms suggested to describe these asymmetries, such as hadronic interactions or electromagnetic interactions in ultra-peripheral collisions, UPC. Events that are correlated with a hard collision indeed display a mostly negative asymmetry that increases in magnitude as a function of transverse momentum with only little dependence on $x_F$. In contrast, events that are not likely to have emerged from a hard collision display positive asymmetries for the nuclear collisions with a kinematic dependence that resembles that of a UPC based model. Because the UPC interaction depends strongly on the charge of the nucleus, those effects are very small for $p+p$ collisions, moderate for $p+$Al collisions, and large for $p+$Au collisions.
Measured forward neutron single spin asymmetries in p+p collisions as a function of pT in bins of xF
Measured forward neutron single spin asymmetries in p+Al collisions as a function of pT in bins of xF
Measured forward neutron single spin asymmetries in p+Au collisions as a function of pT in bins of xF
Presented are the first measurements of the transverse single-spin asymmetries ($A_N$) for neutral pions and eta mesons in $p$+Au and $p$+Al collisions at $\sqrt{s_{_{NN}}}=200$ GeV in the pseudorapidity range $|\eta|<$0.35 with the PHENIX detector at the Relativistic Heavy Ion Collider. The asymmetries are consistent with zero, similar to those for midrapidity neutral pions and eta mesons produced in $p$+$p$ collisions. These measurements show no evidence of additional effects that could potentially arise from the more complex partonic environment present in proton-nucleus collisions.
Data from Figure 2 (a) of the $\pi^{0}$ transverse single-spin asymmetry in $\sqrt{s_{NN}}=200$ GeV $p^{\uparrow}+$Au and $p^{\uparrow}+$Al collisions as a function of $p_{T}$.
Data from Figure 2 (b) of the $\eta$ transverse single-spin asymmetry in $\sqrt{s_{NN}}=200$ GeV $p^{\uparrow}+$Au and $p^{\uparrow}+$Al collisions as a function of $p_{T}$.
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