Jet fragmentation transverse momentum distributions in pp and p-Pb collisions at $$ \sqrt{s} $$, $$ \sqrt{s_{\mathrm{NN}}} $$ = 5.02 TeV

Abstract Jet fragmentation transverse momentum (jT) distributions are measured in proton-proton (pp) and proton-lead (p-Pb) collisions at $$ \sqrt{s_{\mathrm{NN}}} $$ s NN = 5.02 TeV with the ALICE experiment at the LHC. Jets are reconstructed with the ALICE tracking detectors and electromagnetic calorimeter using the anti-kT algorithm with resolution parameter R = 0.4 in the pseudorapidity range |η| < 0.25. The jT values are calculated for charged particles inside a fixed cone with a radius R = 0.4 around the reconstructed jet axis. The measured jT distributions are compared with a variety of parton-shower models. Herwig and Pythia 8 based models describe the data well for the higher jT region, while they underestimate the lower jT region. The jT distributions are further characterised by fitting them with a function composed of an inverse gamma function for higher jT values (called the “wide component”), related to the perturbative component of the fragmentation process, and with a Gaussian for lower jT values (called the “narrow component”), predominantly connected to the hadronisation process. The width of the Gaussian has only a weak dependence on jet transverse momentum, while that of the inverse gamma function increases with increasing jet transverse momentum. For the narrow component, the measured trends are successfully described by all models except for Herwig. For the wide component, Herwig and PYTHIA 8 based models slightly underestimate the data for the higher jet transverse momentum region. These measurements set constraints on models of jet fragmentation and hadronisation.

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Direct Photon Measurements with the ALICE Experiment at the LHC

Proceedings ◽

10.3390/proceedings2019010001 ◽

2019 ◽

Vol 10 (1) ◽

pp. 1

Author(s):

Erwann Masson ◽

on behalf of the ALICE Collaboration

Keyword(s):

Transverse Momentum ◽

High Energy ◽

Direct Photon ◽

High Transverse Momentum ◽

Alice Experiment ◽

Direct Photons ◽

Proton Proton ◽

Small Systems ◽

Energy Hadron

In high-energy hadron collisions, direct photons can be produced in various processes andare of particular interest to study the hot QCD medium since they escape it without being affected.These proceedings present the latest ALICE experiment results concerning direct photon productionin proton-proton (pp), proton-lead (p–Pb) and lead-lead (Pb–Pb) collisions. All measurements agreewith pQCD calculations at high transverse momentum (pT) and show no direct photon excess at lowpT in small systems while a low-pT signal is found in central Pb–Pb collisions.

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Measurement of the inclusive isolated photon production cross section in $$\text{ p }\text{ p }$$ collisions at $$\sqrt{s}=7$$ TeV

The European Physical Journal C ◽

10.1140/epjc/s10052-019-7389-9 ◽

2019 ◽

Vol 79 (11) ◽

Cited By ~ 1

Author(s):

S. Acharya ◽

◽

D. Adamová ◽

S. P. Adhya ◽

A. Adler ◽

...

Keyword(s):

Transverse Momentum ◽

Cross Section ◽

Production Cross Section ◽

Collision Energy ◽

Production Cross ◽

Electromagnetic Calorimeter ◽

Leading Order ◽

Alice Experiment ◽

Momentum Range ◽

Isolated Photons

Abstract The production cross section of inclusive isolated photons has been measured by the ALICE experiment at the CERN LHC in pp collisions at a centre-of-momentum energy of $$\sqrt{s}=$$s= 7 TeV. The measurement is performed with the electromagnetic calorimeter EMCal and the central tracking detectors, covering a range of $$|\eta |<0.27$$|η|<0.27 in pseudorapidity and a transverse momentum range of $$ 10< p_\mathrm {T}^{\gamma }< 60~\mathrm {GeV}/c$$10<pTγ<60GeV/c. The result extends the $$p_\mathrm {T}$$pT coverage of previously published results of the ATLAS and CMS experiments at the same collision energy to smaller $$p_\mathrm {T}$$pT. The measurement is compared to next-to-leading order perturbative QCD calculations and to the results from the ATLAS and CMS experiments. All measurements and theory predictions are in agreement with each other.

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Search for new phenomena in final states with b-jets and missing transverse momentum in $$ \sqrt{\mathrm{s}} $$ = 13 TeV pp collisions with the ATLAS detector

Journal of High Energy Physics ◽

10.1007/jhep05(2021)093 ◽

2021 ◽

Vol 2021 (5) ◽

Author(s):

G. Aad ◽

◽

B. Abbott ◽

D. C. Abbott ◽

A. Abed Abud ◽

...

Keyword(s):

Transverse Momentum ◽

Pair Production ◽

Atlas Detector ◽

Final States ◽

Proton Proton ◽

Missing Transverse Momentum ◽

The Standard Model ◽

Proton Data ◽

Identification Techniques ◽

New Phenomena

Abstract The results of a search for new phenomena in final states with b-jets and missing transverse momentum using 139 fb−1 of proton-proton data collected at a centre-of-mass energy $$ \sqrt{s} $$ s = 13 TeV by the ATLAS detector at the LHC are reported. The analysis targets final states produced by the decay of a pair-produced supersymmetric bottom squark into a bottom quark and a stable neutralino. The analysis also seeks evidence for models of pair production of dark matter particles produced through the decay of a generic scalar or pseudoscalar mediator state in association with a pair of bottom quarks, and models of pair production of scalar third-generation down-type leptoquarks. No significant excess of events over the Standard Model background expectation is observed in any of the signal regions considered by the analysis. Bottom squark masses below 1270 GeV are excluded at 95% confidence level if the neutralino is massless. In the case of nearly mass-degenerate bottom squarks and neutralinos, the use of dedicated secondary-vertex identification techniques permits the exclusion of bottom squarks with masses up to 660 GeV for mass splittings between the squark and the neutralino of 10 GeV. These limits extend substantially beyond the regions of parameter space excluded by similar ATLAS searches performed previously.

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Search for dark matter in association with an energetic photon in pp collisions at $$ \sqrt{s} $$ = 13 TeV with the ATLAS detector

Journal of High Energy Physics ◽

10.1007/jhep02(2021)226 ◽

2021 ◽

Vol 2021 (2) ◽

Author(s):

G. Aad ◽

◽

B. Abbott ◽

D. C. Abbott ◽

A. Abed Abud ◽

...

Keyword(s):

Dark Matter ◽

Transverse Momentum ◽

Standard Model ◽

Confidence Level ◽

Axial Vector ◽

Beyond The Standard Model ◽

Proton Proton ◽

Missing Transverse Momentum ◽

Upper Limits ◽

The Standard Model

Abstract A search for dark matter is conducted in final states containing a photon and missing transverse momentum in proton-proton collisions at $$ \sqrt{s} $$ s = 13 TeV. The data, collected during 2015–2018 by the ATLAS experiment at the CERN LHC, correspond to an integrated luminosity of 139 fb−1. No deviations from the predictions of the Standard Model are observed and 95% confidence-level upper limits between 2.45 fb and 0.5 fb are set on the visible cross section for contributions from physics beyond the Standard Model, in different ranges of the missing transverse momentum. The results are interpreted as 95% confidence-level limits in models where weakly interacting dark-matter candidates are pair-produced via an s-channel axial-vector or vector mediator. Dark-matter candidates with masses up to 415 (580) GeV are excluded for axial-vector (vector) mediators, while the maximum excluded mass of the mediator is 1460 (1470) GeV. In addition, the results are expressed in terms of 95% confidence-level limits on the parameters of a model with an axion-like particle produced in association with a photon, and are used to constrain the coupling gaZγ of an axion-like particle to the electroweak gauge bosons.

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Search for squarks and gluinos in final states with jets and missing transverse momentum using 139 fb−1 of $$ \sqrt{s} $$ = 13 TeV pp collision data with the ATLAS detector

Journal of High Energy Physics ◽

10.1007/jhep02(2021)143 ◽

2021 ◽

Vol 2021 (2) ◽

Cited By ~ 1

Author(s):

G. Aad ◽

◽

B. Abbott ◽

D. C. Abbott ◽

A. Abed Abud ◽

...

Keyword(s):

Transverse Momentum ◽

Hadron Collider ◽

Atlas Detector ◽

Simplified Model ◽

Supersymmetric Particle ◽

Final States ◽

Proton Proton ◽

Missing Transverse Momentum ◽

First And Second Generation ◽

Proton Proton Collisions

Abstract A search for the supersymmetric partners of quarks and gluons (squarks and gluinos) in final states containing jets and missing transverse momentum, but no electrons or muons, is presented. The data used in this search were recorded by the ATLAS experiment in proton-proton collisions at a centre-of-mass energy of $$ \sqrt{s} $$ s = 13 TeV during Run 2 of the Large Hadron Collider, corresponding to an integrated luminosity of 139 fb−1. The results are interpreted in the context of various R-parity-conserving models where squarks and gluinos are produced in pairs or in association and a neutralino is the lightest supersymmetric particle. An exclusion limit at the 95% confidence level on the mass of the gluino is set at 2.30 TeV for a simplified model containing only a gluino and the lightest neutralino, assuming the latter is massless. For a simplified model involving the strong production of mass-degenerate first- and second-generation squarks, squark masses below 1.85 TeV are excluded if the lightest neutralino is massless. These limits extend substantially beyond the region of supersymmetric parameter space excluded previously by similar searches with the ATLAS detector.

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