SearcharxivSearch

arXiv subjects

Yazid Delenda

Publications and source records attributed to Yazid Delenda.

At least 19 recordsLinked to original sources

Constraining non-commutative geometry with W/Z+jet production at the LHC

We present a comprehensive calculation of the squared matrix elements for all partonic channels contributing to $W^\pm/Z$+jet production at hadron colliders within the framework of the non-commutative Standard Model (NCSM), including leptonic decays $W\to eν$ and $Z\to {μ^+μ^-}$. Our computation incorporates both $\mathcal{O}(Θ)$ corrections to the Standard Model vertices and additional interaction terms inherent to the NCSM. A key finding is that the production amplitudes receive first-order corrections at $\mathcal{O}(Θ)$, a distinctive feature compared to many other processes where non-commutative effects enter only at $\mathcal{O}(Θ^2)$. The leptonic decay widths, in contrast, are modified solely at $\mathcal{O}(Θ^2)$. This $\mathcal{O}(Θ)$ enhancement provides improved sensitivity to non-commutative geometry, allowing us to probe for and constrain the non-commutative energy scale in the multi-TeV range. We provide numerical predictions for angular (azimuthal and rapidity) distributions and the forward--backward asymmetry, and compare them to state-of-the-art Standard Model predictions at leading and next-to-leading order from the \texttt{MCFM} Monte Carlo program. Finally, we test the NCSM with experimental data by analyzing an unbinned, particle-level $Z$+jet dataset from the ATLAS experiment. From this data, we calculate the azimuthal spectrum and forward-backward asymmetry, which are then used to derive stringent lower bounds on the non-commutative scale $Λ$. Our analysis accounts for Earth rotation effects by treating the non-commutative tensor as fixed in a celestial frame and deriving time-averaged observables in the rotating detector frame.

hep-ph

Top-quark pair production in electron-positron collisions within the minimal noncommutative Standard Model

We study top-quark pair production in electron-positron collisions within the framework of the minimal noncommutative Standard Model. Noncommutative effects are incorporated using the Seiberg-Witten map, and the scattering squared amplitude for the process $e^+e^-\to t\bar{t}$ is computed consistently up to second order in the noncommutativity parameter $Θ^{μν}$. We derive the total cross-section, the polar and azimuthal angular distributions, and the forward-backward asymmetry, all of which exhibit sensitivity to space-time noncommutativity. Numerical results are evaluated for center-of-mass energies relevant to future linear colliders, such as the ILC and CLIC. Our analysis demonstrates that noncommutative geometry can induce significant characteristic deviations from the Standard Model predictions, offering a potential indirect probe of space-time noncommutativity at high-energy $e^+e^-$ collisions.

hep-ph

Resummed jet mass distribution with trimming in Z+jet events at the LHC

In this paper, we calculate the resummed jet mass distribution up to next-to-leading logarithmic accuracy for jets defined with the trimming groomer in Z+jet events at the LHC. We compute at fixed order and to all orders the large logarithms, both in the jet mass and $z_{\mathrm{cut}}$ trimming variable, including non-global and clustering logarithms. We conduct phenomenological studies at $\mathcal{O}(α_s)$, validating our results by comparing them with the fixed-order Monte Carlo program MCFM, which provides NLO predictions for hadron colliders. The resummation of non-global logarithms is estimated in the large-$\mathrm{N_c}$ limit. Our resummed result is compared to Monte Carlo parton shower simulations from Pythia 8, Herwig ++ and Sherpa 2 event generators.

hep-ph

Transverse momentum and rapidity distributions of top quarks in pair and single top quark production within the non-commutative standard model at the LHC

This paper presents a comprehensive study of top quark phenomenology within the Non-Commutative Standard Model. We calculate non-commutative corrections to the squared amplitudes for top quark pair production, as well as for single top quark production via the $t$-channel and $tW$-channel, while noting that the $s$-channel remains unaffected by non-commutative geometry. Utilizing MadGraph5_aMC@NLO, we determine total cross-sections at various center-of-mass energies and examine differential distributions in transverse momentum and rapidity at leading order in both the strong coupling $α_S$ and the non-commutative parameter $Θ$. For single top production in the $t$-channel, a matching technique is employed to extend the validity of the distribution to low $p_t^{top}$ values through resummation. We also compare the non-commutative corrections with higher-order QCD corrections obtained at NLO using MCFM and at NNLO from existing literature. Our findings reveal significant deviations arising from non-commutative geometry at high energies, providing insights into potential new physics at energy scales accessible by current and future colliders.

hep-ph

Higgs $p_t$ distribution in Higgs + jet production at hadron colliders within the noncommutative effective standard model

We use the noncommutative Higgs effective standard model to make a phenomenological prediction for the transverse momentum distribution of the Higgs boson produced in association with a jet at hadron colliders. We calculate at leading order in the noncommutative parameter $Θ$ as well as leading order in the strong coupling $α_s$, the one-loop $p_t$ distribution of the Higgs boson. As in the standard model, the fixed-order distribution suffers from large logarithms at small $p_t$ which require an all-orders resummation. We find that the large-$p_t$ region of the distribution is strongly affected by the non-commutativity, while small-$p_t$ region is not. Following this observation, we propose a simple matching method that allows us to compute a result that is also valid at small $p_t$ obtained with standard-model parton showers such as Pythia 8. We also compare our results with the next-to-leading order (NLO) and next-to-next-to-leading order (NNLO) distributions in the standard model, in order to assess the importance of higher-order effects in the search for non-commutativity at colliders.

hep-ph

Dijet azimuthal decorrelation in $e^+e^-$ annihilation

We examine non-global and clustering logarithms in the distribution of the azimuthal decorrelation between two jets in $e^+e^-\to$ dijet events, where the jets are defined with $E$-scheme recombination in the generalized $k_t$ algorithm. We calculate at one loop and to all orders the leading global single logarithms in the distribution of the said observable. We also compute at fixed order up to four loops at finite $N_c$ the non-global and clustering logarithms, and numerically resum them to all orders in the large-$N_c$ approximation. We compare our results at $\mathcal{O}(α_s)$ and $\mathcal{O}(α_s^2)$ with those of the EVENT2 fixed-order Monte Carlo program and find agreement of the leading singular behavior of the azimuthal decorrelation distribution. We find that the impact of non-global logarithms on the resummed distribution in the anti-$k_t$ algorithm is substantial, while it is significantly smaller in the $k_t$ algorithm. Furthermore, the combined clustering and non-global logarithms in the $k_t$ algorithm have an even smaller effect on the distribution. Finally, we use the program Gnole to calculate the resummed distribution at NLL accuracy, thus achieving state-of-the-art accuracy for the resummation of this quantity.

hep-ph

Azimuthal decorrelation between a jet and a Z boson at hadron colliders

We revisit the azimuthal decorrelation $δϕ$ between a jet and a $Z$ boson produced at hadron colliders. Employing different recombination schemes for the jets leads to significantly different NLL-resummed predictions for the distribution of this quantity. Specifically when the jets are reconstructed with the $E$-scheme (i.e., four-momentum addition) in the $k_t$ or anti-$k_t$ clustering algorithms, then the resummation becomes highly non-trivial due to the presence of non-global and/or clustering logarithms. We evaluate these logarithms analytically at two loops and numerically to all orders in the large-$\mathrm{N_c}$ limit, and present a full NLL resummation of $δϕ$. We extend the accuracy of the perturbative expansion of the resummed distribution at fixed order to NNLL accuracy by including $\mathcal{O}(α_s)$ NLO corrections obtained with MadGraph5_aMC@NLO. We compare our findings with results of various Monte Carlo event generators and with experimental data from the CMS collaboration.

hep-ph

Jet mass distribution in Higgs/vector boson + jet events at hadron colliders with $k_t$ clustering

We address the issues of clustering and non-global logarithms for jet shapes in the process of production of a Higgs/vector boson associated with a single hard jet at hadron colliders. We perform an analytical fixed-order calculation up to second order in the coupling as well as an all-orders estimation for the specific invariant mass distribution of the highest-$p_t$ jet, for various jet algorithms. Our results are derived in the eikonal (soft) limit and are valid up to next-to-leading logarithmic accuracy. We perform a matching of the resummed distribution to next-to-leading order results from MCFM and compare our findings with the outputs of the Monte Carlo event generators Pythia 8 and Herwig 7. After accounting for non-perturbative effects we compare our results with available experimental data from the CMS collaboration for the Z + jet production. We find good agreement over a wide range of the observable.

hep-ph

Eikonal amplitudes for three-hard legs processes at finite-N$_c$

We extend our previous work on scattering amplitudes [1] to hadron collisions. We provide a general formalism for the computation of eikonal amplitudes squared for the radiation of soft and energy-ordered gluons off three hard-legs at finite-N$_c$ to any order in the perturbative expansion. Examples of three-hard legs processes include vector/Higgs boson production in association with a single hard jet and dijet production in DIS. Explicit expressions for the radiation of up to four gluons are provided as an illustration of the formalism.

hep-ph

Eikonal amplitudes and non-global logarithms from the BMS equation

The Banfi-Marchesini-Smye (BMS) equation accounts for non-global logarithms to all orders in perturbation theory in the large-Nc approximation. We show that the squared amplitudes for the emission of soft energy-ordered gluons are correctly embedded in this equation, and explicitly verify that they coincide with those derived in our previous work in the large-Nc limit up to sixth order in the strong coupling. We perform analytical calculations for the non-global logarithms up to fourth order for the specific hemisphere mass distribution in e+ e- collisions, thus confirming our previous semi-numerical results. We show that the solution to the BMS equation may be cast into a product of an infinite number of exponentials each of which resums a class of Feynman diagrams that manifest a symmetry pattern, and explicitly carry out the computation of the first of these exponentials.

hep-ph

Eikonal gluon bremsstrahlung at finite N_c beyond two loops

We present a general formalism for computing the matrix-element squared for the emission of soft energy-ordered gluons beyond two loops in QCD perturbation theory at finite $N_c$. Our formalism is valid in the eikonal approximation. A Mathematica program has been developed for the automated calculation of all real/virtual eikonal squared amplitudes needed at a given loop order. For the purpose of illustration we show the explicit forms of the eikonal squared amplitudes up to the fifth-loop order. In the large-$N_c$ limit our results coincide with those previously reported in literature.

hep-ph

Negative heat capacity for a Klein-Gordon oscillator in non-commutative complex phase space

We obtain exact solutions to the two-dimensional Klein-Gordon oscillator in a non-commutative complex phase space to first order in the non-commutativity parameter. We derive the exact non-commutative energy levels and show that the energy levels split to $2m$ levels. We find that the non-commutativity plays the role of a magnetic field interacting automatically with the spin of a particle induced by the non-commutativity of complex phase space. The effect of the non-commutativity parameter on the thermal properties is discussed. It is found that the dependence of the heat capacity $C_V$ on the non-commutative parameter gives rise to a negative quantity. Phenomenologically, this effectively confirms the presence of the effects of self-gravitation induced by the non-commutativity of complex phase space.

hep-th

On the resummation of non-global logarithms at finite $\mathbf{N_c}$

We present a calculation of non-global logs at finite $\mathrm{N_c}$ for the hemisphere mass distribution in $e^+e^-\to 2$ jets at single log accuracy up to fifth order in the strong coupling constant. Our results suggest a possible all-orders resummation of these large logs into an exponential. Comparing our results to those at large $\mathrm{N_c}$, recently reported in literature, we find an agreement. We additionally compare our findings with the numerical all-orders resummation at large $\mathrm{N_c}$ and discuss the significance of neglected finite-$\mathrm{N_c}$ corrections on the said distribution.

hep-ph

Eikonal gluon radiation at finite-Nc beyond 2 loops

We present first calculations of QCD matrix-elements in perturbation theory at finite Nc beyond 2 loops in the eikonal approximation for e+ e- annihilation processes. For the emission of n soft energy-ordered gluons we solve both the colour and kinematic structures at a given order in perturbation theory by means of a Mathematica program that relies solely on a recently developed Mathematica code, ColorMath, that evaluates the trace of products of colour matrices. At large Nc, our squared amplitudes reduce to those already known in the literature.

hep-ph

Non-global logarithms at finite Nc beyond leading order

We analytically compute non-global logarithms at finite Nc fully up to 4 loops and partially at 5 loops, for the hemisphere mass distribution in e+e- to di-jets to leading logarithmic accuracy. Our method of calculation relies solely on integrating the eikonal squared-amplitudes for the emission of soft energy-ordered real-virtual gluons over the appropriate phase space. We show that the series of non-global logarithms in the said distribution exhibits a pattern of exponentiation thus confirming - by means of brute force - previous findings. In the large-Nc limit, our results coincide with those recently reported in literature. A comparison of our proposed exponential form with all-orders numerical solutions is performed and the phenomenological impact of the finite-Nc corrections is discussed.

hep-ph

Resummation of clustering logarithms for non-global QCD observables

We address the problem of resumming leading clustering logs in QCD jet observables defined using the k_t, CA and SISCone algorithms. We specifically choose the jet mass distribution as an example and calculate up to order(alpha_s^4) clustering-log terms in the series expansion at single-log accuracy. These terms are found to exhibit a pattern of exponentiation and we are thus able to perform an all-orders analytical resummation for the clustering logs. We also numerically calculate the non-global logs at large N_c. We show that our result for the resummation of clustering logs is a very good analytical approximation to the numerical result obtained using a specialised Monte Carlo program.

hep-ph

Noncommutative of space-time and the relativistic Hydrogen atom

We study the Klein-Gordon equation in a non-commutative space-time as applied to the Hydrogen atom to extract the energy levels, by considering the second-order corrections in the non-commutativity paramete and by comparing to the 2S - 1S transition accuracy we get a bound on the parameter of noncommutativity. Phenomenologically we show that non-commutativity is the source of lamb shift corrections and spin electron.

math-ph

On the resummation of clustering logarithms for non-global observables

Clustering logs have been the subject of much study in recent literature. They are a class of large logs which arise for non-global jet-shape observables where final-state particles are clustered by a non-cone--like jet algorithm. Their resummation to all orders is highly non--trivial due to the non-trivial role of clustering amongst soft gluons which results in the phase-space being non-factorisable. This may therefore significantly impact the accuracy of analytical estimations of many of such observables. Nonetheless, in this paper we address this very issue for jet shapes defined using the $k_t$ and C/A algorithms, taking the jet mass as our explicit example. We calculate the coefficients of the Abelian $α_s^2 L^2$, $α_s^3 L^3$ and $α_s^4 L^4$ NLL terms in the exponent of the resummed distribution and show that the impact of these logs is small which gives confidence on the perturbative estimate without the neglected higher-order terms. Furthermore we numerically resum the non-global logs of the jet mass distribution in the $k_t$ algorithm in the large-$N_c$ limit.

hep-ph