Next-to-next-to-leading order calculation of the strong coupling constant α s by using moments of event-shape variables

Pramana ◽  
2013 ◽  
Vol 81 (5) ◽  
pp. 791-798
Author(s):  
SAMIRA SHOEIBI MOHSENABADI ◽  
MOHAMMAD EBRAHIM ZOMORRODIAN
Keyword(s):  
Strong Coupling ◽  
Strong Coupling Constant ◽  
Event Shape ◽  
Leading Order ◽  
Coupling Constant ◽  
Order Calculation

Measurement of strong coupling constant from transverse momentum

2009 ◽  
Vol 87 (11) ◽  
pp. 1151-1158 ◽  
Author(s):  
Alireza Sepehri ◽  
Tooraj Ghaffary ◽  
Mohammad Ebrahim Zomorrodian
Keyword(s):  
Strong Coupling ◽  
Clustering Algorithm ◽  
Center Of Mass ◽  
Parton Model ◽  
Energy Scale ◽  
Strong Coupling Constant ◽  
Event Shape ◽  
Coupling Constant ◽  
Center Of Mass Energy ◽  
Gluon Bremsstrahlung

Data from e+e– annihilation into hadrons at the center of mass energy of 60 GeV are used to study the distribution of momentum components with respect to the jet axis. At high energies, the gluon emission that leads to three jet structures represents a gross violation of the parton model without gluons and finds a most natural interpretation if gluon bremsstrahlung is included. The coupling constant, αs, is measured by two different methods, first by employing the jet clustering algorithm introduced by the JADE group. Using this method, the strong coupling constant is found to be 0.123 ± 0.004. Next, from the event shape distributions, we extract the strong coupling constant, αs, and test its evaluation with energy scale. The results are consistent with the running of αs, expected from QCD predictions. Averaging over different observables, the value of αs is determined to be 0.121 ± 0.007.

scholarly journals Precise determination of αS( $ m_{Z^0 } $ ) from a global fit of energy-energy correlations to NNLO+NNLL predictions

2019 ◽  
Vol 206 ◽  
pp. 05002
Author(s):  
A. Kardos ◽  
S. Kluth ◽  
G. Somogyi ◽  
Z. Tulipánt ◽  
A. Verbytskyi
Keyword(s):  
Strong Coupling ◽  
Precise Determination ◽  
Strong Coupling Constant ◽  
Final States ◽  
Leading Order ◽  
Coupling Constant ◽  
Global Fit ◽  
Hadronic Final States

We present a determination of the strong coupling constant αS( $ m_{Z^0 } $ ) using a global fit of theory predictions in next-to-next-next-leading-order (NNLO) combined with resummed predictions at the next-to-next-leading-log level (NNLL) [bibrR11]. The predictions are compared to distributions of energy-energy correlations measured in e+e−annihilation to hadronic final states by experiments at the e+e−colliders LEP, PETRA, TRISTAN and PEP. The predictions are corrected for hadronisation effects using the modern generator programs Sherpa 2.2.4 and Herwig 7.1.1.

scholarly journals Tree-level splitting amplitudes for a gluon into four collinear partons

2020 ◽  
Vol 2020 (10) ◽  
Author(s):  
Vittorio Del Duca ◽  
Claude Duhr ◽  
Rayan Haindl ◽  
Achilleas Lazopoulos ◽  
Martin Michel
Keyword(s):  
Scattering Amplitudes ◽  
Strong Coupling ◽  
Strong Coupling Constant ◽  
Tree Level ◽  
Leading Order ◽  
Coupling Constant ◽  
Level Splitting ◽  
Infrared Behaviour

Abstract We compute in conventional dimensional regularisation the tree-level splitting amplitudes for a gluon parent which splits into four collinear partons. This is part of the universal infrared behaviour of the QCD scattering amplitudes at next-to-next-to-next-to-leading order (N3LO) in the strong coupling constant. Combined with our earlier results for a quark parent, this completes the set of tree-level splitting amplitudes required at this order. We also study iterated collinear limits where a subset of the four collinear partons become themselves collinear.

scholarly journals Measurement of the strong coupling constant αs from global event-shape variables of hadronic Z decays

1991 ◽  
Vol 255 (4) ◽  
pp. 623-633 ◽  
Author(s):  
D. Decampo ◽  
B. Deschizeaux ◽  
C. Goy ◽  
J.-P. Lees ◽  
M.-N. Minard ◽  
...  
Keyword(s):  
Strong Coupling ◽  
Strong Coupling Constant ◽  
Event Shape ◽  
Coupling Constant ◽  
Global Event ◽  
Z Decays ◽  
Hadronic Z Decays

scholarly journals Measurement of Strong Coupling Constant by Using Event Shape Moments in Perturbative Theory

2014 ◽  
Vol 45 (5) ◽  
pp. 1077 ◽  
Author(s):  
L. Khajooee ◽  
T. Kalalian ◽  
R. Saleh-Moghaddam ◽  
A. Sepehri ◽  
M.E. Zomorrodian
Keyword(s):  
Strong Coupling ◽  
Strong Coupling Constant ◽  
Event Shape ◽  
Coupling Constant

scholarly journals Erratum to: Determination of the strong coupling constant $${{\varvec{\alpha _{\mathrm{s}} (m_{\mathrm{Z}})}}}$$ in next-to-next-to-leading order QCD using H1 jet cross section measurements

2021 ◽  
Vol 81 (8) ◽  
Author(s):  
◽  
V. Andreev ◽  
A. Baghdasaryan ◽  
K. Begzsuren ◽  
A. Belousov ◽  
...  
Keyword(s):  
Strong Coupling ◽  
Cross Section ◽  
Distribution Functions ◽  
Strong Coupling Constant ◽  
Leading Order ◽  
Coupling Constant ◽  
Parton Distribution Functions ◽  
Section Data ◽  
Dijet Data

AbstractThe determination of the strong coupling constant $$\alpha _{\mathrm{s}} (m_{\mathrm{Z}})$$ α s ( m Z ) from H1 inclusive and dijet cross section data [1] exploits perturbative QCD predictions in next-to-next-to-leading order (NNLO) [2–4]. An implementation error in the NNLO predictions was found [4] which changes the numerical values of the predictions and the resulting values of the fits. Using the corrected NNLO predictions together with inclusive jet and dijet data, the strong coupling constant is determined to be $$\alpha _{\mathrm{s}} (m_{\mathrm{Z}}) =0.1166\,(19)_{\mathrm{exp}}\,(24)_{\mathrm{th}}$$ α s ( m Z ) = 0.1166 ( 19 ) exp ( 24 ) th . Complementarily, $$\alpha _{\mathrm{s}} (m_{\mathrm{Z}})$$ α s ( m Z ) is determined together with parton distribution functions of the proton (PDFs) from jet and inclusive DIS data measured by the H1 experiment. The value $$\alpha _{\mathrm{s}} (m_{\mathrm{Z}}) =0.1147\,(25)_{\mathrm{tot}}$$ α s ( m Z ) = 0.1147 ( 25 ) tot obtained is consistent with the determination from jet data alone. Corrected figures and numerical results are provided and the discussion is adapted accordingly.

scholarly journals Determination of $$\alpha _{S}$$ beyond NNLO using event shape averages

2021 ◽  
Vol 81 (4) ◽  
Author(s):  
Adam Kardos ◽  
Gábor Somogyi ◽  
Andrii Verbytskyi
Keyword(s):  
Monte Carlo ◽  
Perturbative Qcd ◽  
Strong Coupling ◽  
Higher Order ◽  
Strong Coupling Constant ◽  
Monte Carlo Event ◽  
Event Shape ◽  
Coupling Constant

AbstractWe consider a method for determining the QCD strong coupling constant using fits of perturbative predictions for event shape averages to data collected at the LEP, PETRA, PEP and TRISTAN colliders. To obtain highest accuracy predictions we use a combination of perturbative $${{{\mathcal {O}}}}(\alpha _{S}^{3})$$ O ( α S 3 ) calculations and estimations of the $${{{\mathcal {O}}}}(\alpha _{S}^{4})$$ O ( α S 4 ) perturbative coefficients from data. We account for non-perturbative effects using modern Monte Carlo event generators and analytic hadronization models. The obtained results show that the total precision of the $$\alpha _{S}$$ α S determination cannot be improved significantly with the higher-order perturbative QCD corrections alone, but primarily requires a deeper understanding of the non-perturbative effects.

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