The first study of the angular distribution of $\mu^+ \mu^-$ pairs produced in the forward rapidity region via the Drell-Yan reaction $pp \rightarrow \gamma^{*}/Z +X \rightarrow l^+ l^- + X$ is presented, using data collected with the LHCb detector at a centre-of-mass energy of 13TeV, corresponding to an integrated luminosity of 5.1 $\rm{fb}^{-1}$. The coefficients of the five leading terms in the angular distribution are determined as a function of the dimuon transverse momentum and rapidity. The results are compared to various theoretical predictions of the $Z$-boson production mechanism and can also be used to probe transverse-momentum-dependent parton distributions within the proton.
Comparison of the measured angular coefficients with different predictions, as a function of the $ Z $ -boson $ p_{\mathrm{T}}$ , in the rapidity region of $ Z $ -boson $y^Z>2$ and $75<M_{\mu\mu}<105\text{ Ge V /}c^2 $. The total uncertainty (shown in the figure) is dominated by the statistical component. The theoretical predictions correspond to the same $ Z $ -boson $ p_{\mathrm{T}}$ bins as data and the $ p_{\mathrm{T}}$ shifts of the theoretical markers in all plots are for visualization purposes only. {DYTurbo} and ResBos predictions include the theoretical uncertainties. |
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Comparison of the measured angular coefficient $A_{2}$ with different predictions, as a function of the $ Z $ -boson $ p_{\mathrm{T}}$ , in the rapidity region of $ Z $ -boson $y^Z>2$ and $50<M_{\mu\mu}<75\text{ Ge V /}c^2 $ (left), $50<M_{\mu\mu}<75\text{ Ge V /}c^2 $ (middle) and $105<M_{\mu\mu}<120\text{ Ge V /}c^2 $ (right). The total uncertainty (shown in the figure) is dominated by the statistical component. The horizontal positions of the theoretical predictions within the bins are adjusted to increase visibility. {DYTurbo} and ResBos predictions include the theoretical uncertainties. |
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Comparison of the measured angular coefficients with ResBos predictions as a function of the $y^Z$ in the $75<M_{\mu\mu}<105\text{ Ge V /}c^2 $ mass region. The total uncertainty (shown in the figure) is dominated by the statistical component. ResBos predictions include the theoretical uncertainties. |
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Animated gif made out of all figures. |
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The number of selected data candidate events in different $ Z $ boson $ p_{\mathrm{T}}$ and rapidity intervals in the mass region $50<M_{\mu\mu}<120\text{ Ge V /}c^2 $. |
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Summary of measured angular coefficients and regularised uncertainties for $A_{i}$ and $A_{0}-A_2$, in intervals of $ Z $ -boson $ p_{\mathrm{T}}$ , in the region of $ Z $ -boson $y>2$ and $75<M_{\mu\mu}<105\text{ Ge V /}c^2 $. The total systematic uncertainty is shown with the breakdown into its underlying components. Entries marked with `-' indicate that the uncertainty is below 0.0001. |
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Summary of measured angular coefficients and regularised uncertainties for $A_{i}$ and $A_{0}-A_2$, in intervals of $ Z $ -boson rapidity, in the region of $ Z $ -boson $ p_{\mathrm{T}} <100 \text{ Ge V /}c $ and $75<M_{\mu\mu}<105\text{ Ge V /}c^2 $. The total systematic uncertainty is shown with the breakdown into its underlying components. Entries marked with `-' indicate that the uncertainty is below 0.0001. |
Table_3.pdf [67 KiB] HiDef png [181 KiB] Thumbnail [77 KiB] tex code |
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Summary of measured angular coefficients and regularised uncertainties for $A_{2}$, in intervals of $ Z $ -boson $ p_{\mathrm{T}}$ , in the region of $ Z $ -boson $y>2$ and different mass ranges. The total systematic uncertainty is shown with the breakdown into its underlying components. Entries marked with `-' indicate that the uncertainty is below 0.0001. |
Table_4.pdf [67 KiB] HiDef png [266 KiB] Thumbnail [127 KiB] tex code |
Created on 20 April 2024.