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Measurement of $B^0$, $B^0_s$, $B^+$ and $\Lambda^0_b$ production asymmetries in 7 and 8 TeV proton-proton collisions

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Abstract

The $B^0$, $B^0_s$, $B^+$ and $\Lambda^0_b$ hadron production asymmetries are measured using a data sample corresponding to an integrated luminosity of 3.0 fb$^{-1}$, collected by the LHCb experiment in proton-proton collisions at centre-of-mass energies of 7 and 8 TeV. The measurements are performed as a function of transverse momentum and rapidity of the $b$ hadrons within the LHCb detector acceptance. The overall production asymmetries, integrated over transverse momentum and rapidity, are also determined.

Figures and captions

Distributions of $ p_{\rm T} $ and $y$ for background-subtracted (top) $ B ^+ $ , (middle) $ B ^0$ and (bottom) $ B ^0_ s $ decays for data collected in proton-proton collisions at the centre-of-mass energies of (left) 7 and (right) 8 $\mathrm{\,TeV}$ . The binning schemes are superimposed.

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Bu2JpsiK2011_PT_Y.pdf
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Bd2Jps[..].pdf [24 KiB]
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Bd2JpsiKst2011_PT_Y.pdf
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Bd2JpsiKst2012_PT_Y.pdf
Bs2Dsp[..].pdf [23 KiB]
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Distributions of (left) invariant mass and (right) decay time for (top) $ B ^0 \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} K ^{*0} $, (middle) $ B ^0_ s \rightarrow D ^-_ s \pi ^+ $ and (bottom) of invariant mass for $ B ^+ \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} K ^+ $ decays, with the results of the fit overlaid. The data were collected in proton-proton collisions at the centre-of-mass energy of 7 $\mathrm{\,TeV}$ . The contributions of the various background sources are also shown. Below each plot are the normalized residual distributions.

Bd2Jps[..].pdf [34 KiB]
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Bd2JpsiKst2011_mass.pdf
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Bd2JpsiKst2011_time.pdf
Bs2Dsp[..].pdf [36 KiB]
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Bs2Dspi2011_mass.pdf
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Bs2Dspi2011_time.pdf
Bu2Jps[..].pdf [32 KiB]
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Bu2JpsiK2011_mass.pdf

Distributions of (left) invariant mass and (right) decay time for (top) $ B ^0 \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} K ^{*0} $, (middle) $ B ^0_ s \rightarrow D ^-_ s \pi ^+ $ and (bottom) of invariant mass for $ B ^+ \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} K ^+ $ decays, with the results of the fit overlaid. The data were collected in proton-proton collisions at the centre-of-mass energy of 8 $\mathrm{\,TeV}$ . The contributions of the various background sources are also shown. Below each plot are the normalized residual distributions.

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Bd2JpsiKst2012_mass.pdf
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Bd2JpsiKst2012_time.pdf
Bs2Dsp[..].pdf [37 KiB]
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Bs2Dspi2012_mass.pdf
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Bs2Dspi2012_time.pdf
Bu2Jps[..].pdf [32 KiB]
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Bu2JpsiK2012_mass.pdf

Time-dependent raw asymmetries for candidates in the (top) $ B ^0 \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} K ^{*0} $ and (bottom) $ B ^0_ s \rightarrow D ^-_ s \pi ^+ $ signal mass regions with the results of the global fits overlaid. Left and right plots correspond to data recorded in proton-proton collisions at centre-of-mass energies of 7 and 8 $\mathrm{\,TeV}$ , respectively. For the $ B ^0_ s $ decay, the asymmetries are obtained by folding the decay-time distributions into one oscillation period, and the offset $t_{0}= 0.2$ ps corresponds to the selection requirement on the decay time.

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Bd2JpsiKst2011_asym.pdf
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Bs2Dspi2011_asym.pdf
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Bs2Dspi2012_asym.pdf

Dependence of $A_\mathrm{P}(B^+)$, for data collected in proton-proton collisions with centre-of-mass of energies of (top) 7 and (bottom) 8 $\mathrm{\,TeV}$ , on (left) $p_{\rm T}$ and (right) $y$. The results of fits using a straight line with zero (solid line) or floating slope parameter (dashed line) are also shown. The fits take into account the correlations amongst the bins.

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Dependence of $A_\mathrm{P}(B^0)$, for data collected in proton-proton collisions with centre-of-mass of energies of (top) 7 and (bottom) 8 $\mathrm{\,TeV}$ , on (left) $p_{\rm T}$ and (right) $y$. The results of fits using a straight line with zero (solid line) or floating slope parameter (dashed line) are also shown. The fits take into account the correlations amongst the bins.

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AP_y_Bd2JpsiKst2012.pdf

Dependence of $A_\mathrm{P}( B ^0_ s )$, for data collected in proton-proton collisions with centre-of-mass of energies of (top) 7 and (bottom) 8 $\mathrm{\,TeV}$ , on (left) $p_{\rm T}$ and (right) $y$. The results of fits with a straight line with zero (solid line) or floating slope parameter (dashed line) are also shown. The fits take into account the correlations amongst the bins.

AP_pt_[..].pdf [14 KiB]
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AP_pt_Bs2Dspi2011.pdf
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AP_y_Bs2Dspi2011.pdf
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Dependence of $A_\mathrm{P}(\Lambda ^0_ b )$, for data collected in proton-proton collisions with centre-of-mass of energies of (top) 7 and (bottom) 8 $\mathrm{\,TeV}$ , on (left) $p_{\rm T}$ and (right) $y$. The results of fits with a straight line with zero (solid line) or floating slope parameter (dashed line) are also shown. The fits take into account the correlations amongst the bins.

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Tables and captions

Values of the various physical inputs used in the fits, as reported in Ref. [33].

Table_1.pdf [65 KiB]
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Values of signal yields, $A_{\rm P}$ and $A_{\rm D}$ obtained from global fits for the two neutral $ B $ -meson decays under study.

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Values of signal yields and raw asymmetries obtained from global fits in the case of the $ B ^+ \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} K ^+ $ decay.

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Absolute values of systematic uncertainties for integrated production asymmetries. The total systematic uncertainties are obtained by summing the individual contributions in quadrature.

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Values for $m$ and $q$ and their correlation coefficient ($\rho$) obtained from fits to the values reported in Tables 10--17 with a first order polynomial function (FOPF), $A_{\mathrm{P}}(b\,\mathrm{hadron}) = a\,x + b$ with $x = p_{\rm T} ,y$. The label SL indicates the fit to the values with a straight line.

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Values of $A_{\rm P}( B ^0_ s )$ and $A_{\rm P}(\Lambda ^0_ b )$ in each kinematic bin for data collected in proton-proton collisions at centre-of-mass energy of 7 $\mathrm{\,TeV}$ . The first uncertainties are statistical and the second systematic.

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Values of $A_{\rm P}( B ^0_ s )$ and $A_{\rm P}(\Lambda ^0_ b )$ in each kinematic bin for data collected in proton-proton collisions at centre-of-mass energy of 8 $\mathrm{\,TeV}$ . The first uncertainties are statistical and the second systematic.

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Values of the production asymmetries in bins of $ p_{\rm T} $, integrated over $y$, for $ B ^+ $ and $ B ^0$ mesons for data collected in proton-proton collisions at the centre-of-mass energy of 7 $\mathrm{\,TeV}$ . The first uncertainties are statistical and the second systematic. The uncertainties among the bins are correlated due to the external inputs: $A_{ C\!P }( B ^+ \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} K ^+ )$ and $A_{\rm D}(\overline{ K }{} {}^0 )$ for $A_{\rm P}( B ^+ )$, and $|q/p|$ for $A_{\rm P}( B ^0 )$.

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Table_10.pdf

Values of the production asymmetries in bins of $y$, integrated over $ p_{\rm T} $, for $ B ^+ $ and $ B ^0$ mesons for data collected in proton-proton collisions at the centre-of-mass energy of 7 $\mathrm{\,TeV}$ . The first uncertainties are statistical and the second systematic. The uncertainties among the bins are correlated due to the external inputs: $A_{ C\!P }( B ^+ \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} K ^+ )$ and $A_{\rm D}(\overline{ K }{} {}^0 )$ for $A_{\rm P}( B ^+ )$, and $|q/p|$ for $A_{\rm P}( B ^0 )$.

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Table_11.pdf

Values of the production asymmetries in bins of $ p_{\rm T} $, integrated over $y$, for $ B ^+ $ and $ B ^0$ mesons for data collected in proton-proton collisions at the centre-of-mass energy of 8 $\mathrm{\,TeV}$ . The first uncertainties are statistical and the second systematic. The uncertainties among the bins are correlated due to the external inputs: $A_{ C\!P }( B ^+ \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} K ^+ )$ and $A_{\rm D}(\overline{ K }{} {}^0 )$ for $A_{\rm P}( B ^+ )$, and $|q/p|$ for $A_{\rm P}( B ^0 )$.

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Table_12.pdf

Values of the production asymmetries in bins of $y$, integrated over $ p_{\rm T} $, for $ B ^+ $ and $ B ^0$ mesons for data collected in proton-proton collisions at the centre-of-mass energy of 8 $\mathrm{\,TeV}$ . The first uncertainties are statistical and the second systematic. The uncertainties among the bins are correlated due to the external inputs: $A_{ C\!P }( B ^+ \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} K ^+ )$ and $A_{\rm D}(\overline{ K }{} {}^0 )$ for $A_{\rm P}( B ^+ )$, and $|q/p|$ for $A_{\rm P}( B ^0 )$.

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Values of the production asymmetries in bins of $ p_{\rm T} $, integrated over $y$, for the $ B ^0_ s $ meson and the $\Lambda ^0_ b $ baryon for data collected in proton-proton collisions at the centre-of-mass energy of 7 $\mathrm{\,TeV}$ . The first uncertainties are statistical and the second systematic. The uncertainties among the bins are correlated due to the external inputs: $A_{ C\!P }( B ^+ \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} K ^+ )$, $A_{\rm D}(\overline{ K }{} {}^0 )$, $|q/p|_{ B ^0 }$ and $|q/p|_{ B ^0_ s }$ for $A_{\rm P}(\Lambda ^0_ b )$, and $|q/p|_{ B ^0_ s }$ for $A_{\rm P}( B ^0_ s )$.

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Values of the production asymmetries in bins of $y$, integrated over $ p_{\rm T} $, for the $ B ^0_ s $ meson and the $\Lambda ^0_ b $ baryon for data collected in proton-proton collisions at the centre-of-mass energy of 7 $\mathrm{\,TeV}$ . The first uncertainties are statistical and the second systematic. The uncertainties among the bins are correlated due to the external inputs: $A_{ C\!P }( B ^+ \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} K ^+ )$, $A_{\rm D}(\overline{ K }{} {}^0 )$, $|q/p|_{ B ^0 }$ and $|q/p|_{ B ^0_ s }$ for $A_{\rm P}(\Lambda ^0_ b )$, and $|q/p|_{ B ^0_ s }$ for $A_{\rm P}( B ^0_ s )$.

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Values of the production asymmetries in bins of $ p_{\rm T} $, integrated over $y$, for the $ B ^0_ s $ meson and the $\Lambda ^0_ b $ baryon for data collected in proton-proton collisions at the centre-of-mass energy of 8 $\mathrm{\,TeV}$ . The first uncertainties are statistical and the second systematic. The uncertainties among the bins are correlated, due to the external inputs: $A_{ C\!P }( B ^+ \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} K ^+ )$, $A_{\rm D}(\overline{ K }{} {}^0 )$, $|q/p|_{ B ^0 }$ and $|q/p|_{ B ^0_ s }$, for $A_{\rm P}(\Lambda ^0_ b )$ and $|q/p|_{ B ^0_ s }$ for $A_{\rm P}( B ^0_ s )$.

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Values of the production asymmetries in bins of $y$, integrated over $ p_{\rm T} $, for the $ B ^0_ s $ meson and the $\Lambda ^0_ b $ baryon for data collected in proton-proton collisions at the centre-of-mass energy of 8 $\mathrm{\,TeV}$ . The first uncertainties are statistical and the second systematic. The uncertainties among the bins are correlated, due to the external inputs: $A_{ C\!P }( B ^+ \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} K ^+ )$, $A_{\rm D}(\overline{ K }{} {}^0 )$, $|q/p|_{ B ^0 }$ and $|q/p|_{ B ^0_ s }$, for $A_{\rm P}(\Lambda ^0_ b )$ and $|q/p|_{ B ^0_ s }$ for $A_{\rm P}( B ^0_ s )$.

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Created on 09 December 2018.Citation count from INSPIRE on 18 December 2018.