Search results for "hadron"
showing 10 items of 3505 documents
A$_{FB}$ in the SMEFT: precision Z physics at the LHC
2021
We study the forward-backward asymmetry $A_{FB}$ in $pp \to \ell^+\ell^-$ at the Z peak within the Standard Model Effective Field Theory (SMEFT). We find that this observable provides per mille level constraints on the vertex corrections of the Z boson to quarks,which close a flat direction in the electroweak precision SMEFT fit. Moreover, we show that current $A_{FB}$ data is precise enough so that its inclusion in the fit improves significantly LEP bounds even in simple New Physics setups. This demonstrates that the LHC can compete with and complement LEP when it comes to precision measurements of the Z boson properties
Parton distributions and lattice QCD calculations: A community white paper
2018
Progress in particle and nuclear physics 100, 107 - 160 (2018). doi:10.1016/j.ppnp.2018.01.007
Multiplicities of charged pions and charged hadrons from deep-inelastic scattering of muons off an isoscalar target
2017
Multiplicities of charged pions and charged hadrons produced in deep-inelastic scattering were measured in three-dimensional bins of the Bjorken scaling variable x , the relative virtual-photon energy y and the relative hadron energy z . Data were obtained by the COMPASS Collaboration using a 160GeV muon beam and an isoscalar target ( 6 LiD). They cover the kinematic domain in the photon virtuality Q2>1(GeV/c)2 , 0.004 1(GeV/c$)^2$, $0.004 < x < 0.4$, $0.2 < z < 0.85$ and $0.1 < y < 0.7$. In addition, a leading-order pQCD analysis was performed using the pion multiplicity results to extract quark fragmentation functions.
Search for the t and b' quarks in hadronic decays of the Z0 boson
1990
We present a search for the third generation up type quark t and a possible fourth down type quark b' in hadronic Z0 decays observed in DELPHI at the LEP collider. For any scenario with a decay through the charged current or into a charged Higgs with a mass at least 6 GeV/c2 below the t and 3 GeVc2 below the b' mass, we set a lower limit for the t quark mass at 44.0 GeV/c2 and for the b' mass at 44.5 GeV/c2. For specific scenarios the mass limits are slightly higher, e.g. for charged current decays the limits are 44.5 and 45.0 GeV/c2 respectively, where all limits are given at a 95% confidence level. © 1990.
Collins asymmetries in inclusive chargedKKandKπpairs produced ine+e−annihilation
2015
We present measurements of Collins asymmetries in the inclusive process e^+e^− → h_1h_2X, h_1h_2 = KK, Kπ, ππ, at the center-of-mass energy of 10.6 GeV, using a data sample of 468 fb^(−1) collected by the BABAR experiment at the PEP-II B factory at SLAC National Accelerator Center. Considering hadrons in opposite thrust hemispheres of hadronic events, we observe clear azimuthal asymmetries in the ratio of unlike sign to like sign, and unlike sign to all charged h_1h_2 pairs, which increase with hadron energies. The Kπ asymmetries are similar to those measured for the ππ pairs, whereas those measured for high-energy KK pairs are, in general, larger.
A search for new physics in dijet mass and angular distributions in pp collisions at [subscript √s=7] TeV measured with the ATLAS detector
2011
A search for new interactions and resonances produced in LHC proton–proton (pp) collisions at a centre-of-mass energy ps = 7 TeV was performed with the ATLAS detector. Using a dataset with an integrated luminosity of 36 pb−1, dijet mass and angular distributions were measured up to dijet masses of 3.5 TeV and were found to be in good agreement with Standard Model predictions. This analysis sets limits at 95% CL on various models for new physics: an excited quark is excluded for mass between 0.60 and 2.64 TeV, an axigluon hypothesis is excluded for axigluon masses between 0.60 and 2.10 TeV and quantum black holes are excluded in models with six extra space–time dimensions for quantum gravity…
Energy dependence of the differences between the quark and gluon jet fragmentation
1996
Three jet events arising from decays of the Z beson, collected by the DELPHI detector, were used to measure differences in quark and gluon fragmentation. Gluon jets were anti-tagged by identifying b quark jets. Unbiased quark jets came from events with two jets plus one photon. Quark and gluon jet properties in different energy ranges were compared for the first time within the same detector. Quark and gluon jets of nearly the same energy in symmetric three jet event topologies were also compared. Using three independent methods, the average value of the ratio of the mean charged multiplicities of gluon and quark jets is [ r ] = 1.241 +/- 0.015 (stat.) +/- 0.025 (syst.). Gluon jets are broa…
Tevatron constraints on models of the Higgs boson with exotic spin and parity using decays to bottom-antibottom quark pairs.
2015
et al.
Hadroproduction of open heavy flavour for PDF analyses
2019
Due to the large masses of the charm and bottom quarks, their production cross sections are calculable within the perturbative QCD. This makes the heavy-quark mesons important observables in high-energy collisions of protons and nuclei. However, the available calculations for heavy-flavored-meson hadroproduction have been somewhat problematic in reliably describing the cross sections across the full kinematic range from zero to very high $p_{\rm T}$. This has put some question marks on the robustness of LHC heavy-flavored-meson measurements in studying the partonic structure of the colliding hadrons and nuclei. Here, we introduce SACOT-$m_{\rm T}$ - a novel scheme for open heavy-flavour had…
On the implementation of NLO high energy factorization in single inclusive forward hadron production
2017
Single inclusive particle production cross sections in high energy hadron collisions at forward rapidity are an important benchmark process for the CGC picture of small x QCD. Recent calculations of this process have not led to a stable perturbative expansion for this quantity at high transverse momenta. We consider the quark channel production cross section using the new rapidity factorization procedure proposed by Iancu et al. We show that for fixed coupling one does indeed obtain a physically meaningful cross section which is positive and reduces in a controlled way to previous leading order calculations. We also consider a running coupling that depends on the transverse momentum of the …