Measurement of the impact-parameter dependent azimuthal anisotropy in coherent $\rho^0$ photoproduction in Pb$-$Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV

The ALICE collaboration Acharya, Shreyasi ; Adamova, Dagmar ; Agarwal, Apar ; et al.
Phys.Lett.B 858 (2024) 139017, 2024.
Inspire Record 2789555 DOI 10.17182/hepdata.154177

This Letter presents the first measurement of the impact-parameter dependent angular anisotropy in the decay of coherently photoproduced $\rho^0$ mesons. The $\rho^0$ mesons are reconstructed through their decay into pion pairs. The measured anisotropy corresponds to the amplitude of the $\cos(2\phi)$ modulation, where $\phi$ is the angle between the two vectors formed by the sum and the difference of the transverse momenta of the pions, respectively. The measurement was performed by the ALICE Collaboration at the LHC using data from ultraperipheral Pb$-$Pb collisions at a center-of-mass energy of $\sqrt{s_{\mathrm{NN}}}~=~5.02$ TeV per nucleon pair. Different impact-parameter regions are selected by classifying the events in nuclear-breakup classes. The amplitude of the $\cos(2\phi)$ modulation is found to increase by about one order of magnitude from large to small impact parameters. Theoretical calculations describe the measured $\cos(2\phi)$ anisotropy and its impact-parameter dependence as the result of a quantum interference effect at the femtometer scale, arising from the ambiguity regarding which of the nuclei is the photon source in the interaction.

1 data table

Amplitudes of the $\cos(2\phi)$ modulation of the $ρ^0$ yield in ultra-peripheral Pb--Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV in all neutron classes.


First measurement of the forward-backward asymmetry in bottom-quark pair production at high mass

The CDF collaboration Aaltonen, Timo Antero ; Amerio, Silvia ; Amidei, Dante E ; et al.
Phys.Rev.D 92 (2015) 032006, 2015.
Inspire Record 1364882 DOI 10.17182/hepdata.73682

We measure the particle-level forward-backward production asymmetry in $b\bar{b}$ pairs with masses $m(b\bar{b})$ larger than 150 GeV/$c^2$, using events with hadronic jets and employing jet charge to distinguish $b$ from $\bar{b}$. The measurement uses 9.5/fb of ppbar collisions at a center of mass energy of 1.96 TeV recorded by the CDF II detector. The asymmetry as a function of $m(b\bar{b})$ is consistent with zero, as well as with the predictions of the standard model. The measurement disfavors a simple model including an axigluon with a mass of 200 GeV/$c^2$ whereas a model containing a heavier 345 GeV/$c^2$ axigluon is not excluded.

1 data table

Values of maximum a posteriori signal asymmetry as a function of $b\bar{b}$ mass. The error bars represent the 68% credible intervals.


Measurement of the production and lepton charge asymmetry of $\textit{W}$ bosons in Pb+Pb collisions at $\sqrt{s_{\mathrm{\mathbf{NN}}}}=$ 2.76 TeV with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Brad ; Abdallah, Jalal ; et al.
Eur.Phys.J.C 75 (2015) 23, 2015.
Inspire Record 1311623 DOI 10.17182/hepdata.66358

A measurement of $\textit{W}$ boson production in lead-lead collisions at $\sqrt{s_{\mathrm{NN}}}=$2.76 TeV is presented. It is based on the analysis of data collected with the ATLAS detector at the LHC in 2011 corresponding to an integrated luminosity of 0.14 $\mathrm{nb}^{-1}$ and 0.15 $\mathrm{nb}^{-1}$ in the muon and electron decay channels, respectively. The differential production yields and lepton charge asymmetry are each measured as a function of the average number of participating nucleons $< N_{\mathrm{part}} >$ and absolute pseudorapidity of the charged lepton. The results are compared to predictions based on next-to-leading-order QCD calculations. These measurements are, in principle, sensitive to possible nuclear modifications to the parton distribution functions and also provide information on scaling of $\textit{W}$ boson production in multi-nucleon systems.

5 data tables

Ratio of W+ and W- candidates in $W\rightarrow \ell \nu_{\ell}$ as a function of the mean number of participants $N_{part}$.

$W^\pm$ boson production yield per binary collision as a function of the mean number of participants $N_{part}$.

Differential production yield per binary collision for $W^{+}$ bosons as a function of $|\eta_\ell|$.

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Measurement of the inclusive leptonic asymmetry in top-quark pairs that decay to two charged leptons at CDF

The CDF collaboration Aaltonen, Timo Antero ; Amerio, Silvia ; Amidei, Dante E ; et al.
Phys.Rev.Lett. 113 (2014) 042001, 2014.
Inspire Record 1290358 DOI 10.17182/hepdata.64422

We measure the inclusive forward-backward asymmetry of the charged-lepton pseudorapidities from top-quark pairs produced in proton-antiproton collisions, and decaying to final states that contain two charged leptons (electrons or muons), using data collected with the Collider Detector at Fermilab. With an integrated luminosity of 9.1 $\rm{fb}^{-1}$, the leptonic forward-backward asymmetry, $A_{\text{FB}}^{\ell}$, is measured to be $0.072 \pm 0.060$ and the leptonic pair forward-backward asymmetry, $A_{\text{FB}}^{\ell\ell}$, is measured to be $0.076 \pm 0.082$, compared with the standard model predictions of $A_{\text{FB}}^{\ell} = 0.038 \pm 0.003$ and $A_{\text{FB}}^{\ell\ell} = 0.048 \pm 0.004$, respectively. Additionally, we combine the $A_{\text{FB}}^{\ell}$ result with a previous determination from a final state with a single lepton and hadronic jets and obtain $A_{\text{FB}}^{\ell} = 0.090^{+0.028}_{-0.026}$.

3 data tables

The leptonic forward-backward asymmetry.

The leptonic pair forward-backward asymmetry.

The leptonic forward-backward asymmetry calculated as the combination of the current asymmetry measurement and a previous CDF measurement.


Indirect measurement of $\sin^2 \theta_W$ (or $M_W$) using $\mu^+\mu^-$ pairs from $\gamma^*/Z$ bosons produced in $p\bar{p}$ collisions at a center-of-momentum energy of 1.96 TeV

The CDF collaboration Aaltonen, Timo Antero ; Amerio, Silvia ; Amidei, Dante E ; et al.
Phys.Rev.D 89 (2014) 072005, 2014.
Inspire Record 1280719 DOI 10.17182/hepdata.64738

Drell-Yan lepton pairs are produced in the process $p\bar{p} \rightarrow \mu^+\mu^- + X$ through an intermediate $\gamma^*/Z$ boson. The forward-backward asymmetry in the polar-angle distribution of the $\mu^-$ as a function of the invariant mass of the $\mu^+\mu^-$ pair is used to obtain the effective leptonic determination $\sin^2 \theta^{lept}_{eff}$ of the electroweak-mixing parameter $\sin^2 \theta_W$, from which the value of $\sin^2 \theta_W$ is derived assuming the standard model. The measurement sample, recorded by the Collider Detector at Fermilab (CDF), corresponds to 9.2 fb-1 of integrated luminosity from $p\bar{p}$ collisions at a center-of-momentum energy of 1.96 TeV, and is the full CDF Run II data set. The value of $\sin^2 \theta^{lept}_{eff}$ is found to be 0.2315 +- 0.0010, where statistical and systematic uncertainties are combined in quadrature. When interpreted within the context of the standard model using the on-shell renormalization scheme, where $\sin^2 \theta_W = 1 - M_W^2/M_Z^2$, the measurement yields $\sin^2 \theta_W$ = 0.2233 +- 0.0009, or equivalently a W-boson mass of 80.365 +- 0.047 GeV/c^2. The value of the W-boson mass is in agreement with previous determinations in electron-positron collisions and at the Tevatron collider.

4 data tables

The measured value of SIN**2(THETAEFF(LEPTON)).

The measured value of SIN**2(THETA(W)).

The measured value of M(W).

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