Measurement of forward W and Z boson production in $pp$ collisions at $ \sqrt{s}=8 $ TeV

The LHCb collaboration Aaij, Roel ; Abellán Beteta, Carlos ; Adeva, Bernardo ; et al.
JHEP 1601 (2016) 155, 2016.
Inspire Record 1406555 DOI 10.17182/hepdata.71419

Measurements are presented of electroweak boson production using data from pp collisions at a centre-of-mass energy of $ \sqrt{s}=8 $ TeV. The analysis is based on an integrated luminosity of 2.0 fb$^{−1}$ recorded with the LHCb detector. The bosons are identified in the W → μν and Z → μ$^{+}$ μ$^{−}$ decay channels. The cross-sections are measured for muons in the pseudorapidity range 2.0 < η < 4.5, with transverse momenta p$_{T}$ > 20 GeV/c and, in the case of the Z boson, a dimuon mass within $ 60 < {M}_{\mu }{{{}_{{}^{+}}}_{\mu}}_{{}^{-}}<120 $ GeV/c$^{2}$. The results are $ {\sigma}_W{{}_{{}^{+}}}_{\to \mu }{{}_{{}^{+}}}_{\nu }=1093.6\pm 2.1\pm 7.2\pm 10.9\pm 12.7\ \mathrm{p}\mathrm{b}, $ $ {\sigma}_W{{}_{{}^{-}}}_{\to \mu }{{}_{{}^{-}}}_{\overline{\nu}}=818.4\pm 1.9\pm 5.0\pm 7.0\pm 9.5\ \mathrm{p}\mathrm{b}, $ $ {\sigma}_{\mathrm{Z}\to \mu }{{{}_{{}^{+}}}_{\mu}}_{{}^{-}}=95.0\pm 0.3\pm 0.7\pm 1.1\pm 1.1\ \mathrm{p}\mathrm{b}, $ $ {\sigma}_{Z\to \mu }{{{}_{{}^{+}}}_{\mu}}_{{}^{-}}=95.0\pm 0.3\pm 0.7\pm 1.1\pm 1.1\ \mathrm{p}\mathrm{b}, $ where the first uncertainties are statistical, the second are systematic, the third are due to the knowledge of the LHC beam energy and the fourth are due to the luminosity determination. The evolution of the W and Z boson cross-sections with centre-of-mass energy is studied using previously reported measurements with 1.0 fb$^{−1}$ of data at 7 TeV. Differential distributions are also presented. Results are in good agreement with theoretical predictions at next-to-next-to-leading order in perturbative quantum chromodynamics.

23 data tables

Inclusive cross-section for $W^+$ and $W^-$ boson production in bins of muon pseudorapidity. The uncertainties are statistical, systematic, beam and luminosity.

Inclusive cross-section for $Z$ boson production in bins of rapidity. The uncertainties are statistical, systematic, beam and luminosity.

Inclusive cross-section for $Z$ boson production in bins of transverse momentum. The uncertainties are statistical, systematic, beam and luminosity.

More…

Measurement of the forward-backward asymmetry in $Z/\gamma^{\ast} \rightarrow \mu^{+}\mu^{-}$ decays and determination of the effective weak mixing angle

The LHCb collaboration Aaij, Roel ; Adeva, Bernardo ; Adinolfi, Marco ; et al.
JHEP 1511 (2015) 190, 2015.
Inspire Record 1394859 DOI 10.17182/hepdata.76490

The forward-backward charge asymmetry for the process $ q\overline{q}\to Z/{\gamma}^{\ast}\to {\mu}^{+}{\mu}^{-} $ is measured as a function of the invariant mass of the dimuon system. Measurements are performed using proton proton collision data collected with the LHCb detector at $ \sqrt{s}=7 $ and 8 TeV, corresponding to integrated luminosities of 1 fb$^{−1}$ and 2 fb$^{−1}$ respectively. Within the Standard Model the results constrain the effective electroweak mixing angle to be $ { \sin}^2{\theta}_{\mathrm{W}}^{\mathrm{eff}}=0.23142\pm 0.00073\pm 0.00052\pm 0.00056, $ where the first uncertainty is statistical, the second systematic and the third theoretical. This result is in agreement with the current world average, and is one of the most precise determinations at hadron colliders to date.

2 data tables

Values for $A_{\rm{FB}}$ with the statistical and positive and negative systematic uncertainties for $\sqrt{s}$ = 7 TeV data. The theoretical uncertainties presented in this table, corresponding to the PDF, scale and FSR uncertainties described in Sec. 5, affect only the predictions of $A_{\rm{FB}}$ and the sin$^2\theta^{\rm{eff}}_{\rm W}$ determination, and do not apply to the uncertainties on the measured $A_{\rm{FB}}$.

Values for $A_{\rm{FB}}$ with the statistical and positive and negative systematic uncertainties for $\sqrt{s}$ = 8 TeV data. The theoretical uncertainties presented in this table, corresponding to the PDF, scale and FSR uncertainties described in Sec. 5, affect only the predictions of $A_{\rm{FB}}$ and the sin$^2\theta^{\rm{eff}}_{\rm W}$ determination, and do not apply to the uncertainties on the measured $A_{\rm{FB}}$.


Measurement of the forward $Z$ boson production cross-section in $pp$ collisions at $\sqrt{s}=7$ TeV

The LHCb collaboration Aaij, Roel ; Adeva, Bernardo ; Adinolfi, Marco ; et al.
JHEP 1508 (2015) 039, 2015.
Inspire Record 1373300 DOI 10.17182/hepdata.2114

A measurement of the production cross-section for Z bosons that decay to muons is presented. The data were recorded by the LHCb detector during pp collisions at a centre-of-mass energy of 7 TeV, and correspond to an integrated luminosity of 1.0 fb$^{−1}$. The cross-section is measured for muons in the pseudorapidity range 2.0 < η < 4.5 with transverse momenta p$_{T}$ > 20 GeV/c. The dimuon mass is restricted to 60 < M$_{μ}$ +$_{μ}$ − < 120 GeV/c$^{2}$. The measured cross-section is $ {\sigma}_{Z\to \mu }{+}_{\mu }-=\left(76.0\pm 0.3\pm 0.5\pm 1.0\pm 1.3\right)\mathrm{p}\mathrm{b} $

11 data tables

Inclusive cross-section for $Z$ boson production in bins of rapidity. The uncertainties are statistical, systematic, beam and luminosity.

Inclusive cross-section for $Z$ boson production in bins of transverse momentum. The uncertainties are statistical, systematic, beam and luminosity.

Inclusive cross-section for $Z$ boson production in bins of PHI*. The uncertainties are statistical, systematic, beam and luminosity.

More…

Study of $W$ boson production in association with beauty and charm

The LHCb collaboration Aaij, Roel ; Adeva, Bernardo ; Adinolfi, Marco ; et al.
Phys.Rev. D92 (2015) 052001, 2015.
Inspire Record 1370436 DOI 10.17182/hepdata.73718

The associated production of a W boson with a jet originating from either a light parton or heavy-flavor quark is studied in the forward region using proton-proton collisions. The analysis uses data corresponding to integrated luminosities of 1.0 and 2.0  fb-1 collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV, respectively. The W bosons are reconstructed using the W→μν decay and muons with a transverse momentum, pT, larger than 20 GeV in the pseudorapidity range 2.0<η<4.5. The partons are reconstructed as jets with pT>20  GeV and 2.2<η<4.2. The sum of the muon and jet momenta must satisfy pT>20  GeV. The fraction of W+jet events that originate from beauty and charm quarks is measured, along with the charge asymmetries of the W+b and W+c production cross sections. The ratio of the W+jet to Z+jet production cross sections is also measured using the Z→μμ decay. All results are in agreement with Standard Model predictions.

1 data table

Summary of the results. All results are reported within a fiducial region that requires a jet with $p_\rm{T} > 20$ GeV in the pseudorapidity range $2.2 < \eta < 4.2$, a muon with $p_\rm{T} > 20$ GeV in the pseudorapidity range $2.0 < \eta < 4.5$, $p_\rm{T}(\mu+j) > 20$ GeV, and $\Delta R(\mu, j) > 0.5$. For $Z+$jet events both muons must fulfill the muon requirements and $60 < M(\mu\mu) < 120$ GeV; the $Z+$jet fiducial region does not require $p_\rm{T}(\mu+j) > 20$ GeV.


Measurement of forward $\rm Z\rightarrow e^+e^-$ production at $\sqrt{s}=8$ TeV

The LHCb collaboration Aaij, Roel ; Adeva, Bernardo ; Adinolfi, Marco ; et al.
JHEP 1505 (2015) 109, 2015.
Inspire Record 1347133 DOI 10.17182/hepdata.73305

A measurement of the cross-section for Z-boson production in the forward region of pp collisions at 8 TeV centre-of-mass energy is presented. The measurement is based on a sample of Z → e$^{+}$e$^{−}$ decays reconstructed using the LHCb detector, corresponding to an integrated luminosity of 2.0 fb$^{−1}$. The acceptance is defined by the requirements 2.0 < η < 4.5 and p$_{T}$ > 20 GeV for the pseudorapidities and transverse momenta of the leptons. Their invariant mass is required to lie in the range 60-120 GeV. The cross-section is determined to be $ \sigma \left(\mathrm{pp}\to \mathrm{Z}\to {\mathrm{e}}^{+}{\mathrm{e}}^{-}\right)=93.81\pm 0.41\left(\mathrm{stat}\right)\pm 1.48\left(\mathrm{syst}\right)\pm 1.14\left(\mathrm{lumi}\right)\mathrm{p}\mathrm{b}, $ where the first uncertainty is statistical and the second reflects all systematic effects apart from that arising from the luminosity, which is given as the third uncertainty. Differential cross-sections are presented as functions of the Z-boson rapidity and of the angular variable ϕ$^{∗}$, which is related to the Z-boson transverse momentum.

3 data tables

Integrated cross-section for Z$\to$ e$^+$e$^-$ within the LHCb acceptance.

Differential cross-section for Z$\to$ e$^+$e$^-$ as a function of Z-boson rapidity. The first error is statistical, the second the uncorrelated experimental systematic, the third the correlated experimental systematic and the last error is the uncertainty in luminosity. The cross-sections are at the Born level, i.e. before FSR. The rightmost column gives values of the additional factor, $f_{\rm FSR}$, by which the results should be multiplied in order to give the cross-sections after FSR.

Differential cross-section for Z$\to$ e$^+$e$^-$ as a function of $\phi^*$. The first error is statistical, the second the uncorrelated experimental systematic, the third the correlated experimental systematic and the last error is the uncertainty in luminosity. The cross-sections are at the Born level, i.e. before FSR. The rightmost column gives values of the additional factor, $f_{\rm FSR}$, by which the results should be multiplied in order to give the cross-sections after FSR.


Observation of associated production of a Z boson with a D meson in the forward region

The LHCb collaboration Aaij, Roel ; Adeva, Bernardo ; Adinolfi, Marco ; et al.
JHEP 1404 (2014) 091, 2014.
Inspire Record 1277075 DOI 10.17182/hepdata.61396

A search for associated production of a $Z$ boson with an open charm meson is presented using a data sample, corresponding to an integrated luminosity of $1.0\,\mathrm{fb}^{-`}$ of proton--proton collisions at a centre-of-mass energy of 7\,TeV, collected by the LHCb experiment. %% Seven candidate events for associated production of a $Z$ boson with a $D^0$ meson and four candidate events for a $Z$ boson with a $D^+$ meson are observed with a combined significance of 5.1standard deviations. The production cross-sections in the forward region are measured to be $$\sigma_{Z\rightarrow\mu^+\mu^-\!,D^0} = 2.50\pm1.12\pm0.22pb$$ $$\sigma_{Z\rightarrow\mu^+\mu^-\!,D^+} = 0.44\pm0.23\pm0.03pb,$$ where the first uncertainty is statistical and the second systematic.

1 data table

Cross-sections in the fiducial region for associated production of a Z boson and a D meson.