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Zooplankton phototaxis in oceanic squid fishing grounds in the Arabian Sea

1528-1532<span style="font-size:9.0pt;mso-bidi-font-size: 11.0pt;font-family:" times="" new="" roman","serif";mso-fareast-font-family:"times="" roman";="" color:black;mso-ansi-language:en-gb;mso-fareast-language:en-us;mso-bidi-language:="" hi"="" lang="EN-GB">Effects of night-illumination on zooplankton abundance were compared with day/night variations in oceanic squid fishing grounds in central Arabian Sea. Zooplankton abundance sh<span style="font-size:9.0pt; mso-bidi-font-size:11.0pt;font-family:" times="" new="" roman","serif";mso-fareast-font-family:="" "times="" roman";color:black;mso-ansi-language:en-gb;mso-fareast-language:="" en-us;mso-bidi-language:ml"="" lang="EN-GB">owed significant variation in relation to three different light conditions with 52% of the total abundance happening during night and 25% during night with illumination. Siphonophores, chaetognaths, copepods and decapod larvae displayed negative phototaxis. Present results indicate that the <span style="font-size:9.0pt;mso-bidi-font-size:11.0pt; font-family:" times="" new="" roman","serif";mso-fareast-font-family:"times="" roman";="" color:black;mso-ansi-language:en-gb;mso-fareast-language:en-us;mso-bidi-language:="" ml"="" lang="EN-GB">response to light stimulus observed among the zooplankton groups were mostly due to the prey-seeking or predator avoidance behavior.</span

Direct observation of the dead-cone effect in quantum chromodynamics

At particle collider experiments, elementary particle interactions with large momentum transfer produce quarks and gluons (known as partons) whose evolution is governed by the strong force, as described by the theory of quantum chromodynamics (QCD) [1]. The vacuum is not transparent to the partons and induces gluon radiation and quark pair production in a process that can be described as a parton shower [2]. Studying the pattern of the parton shower is one of the key experimental tools in understanding the properties of QCD. This pattern is expected to depend on the mass of the initiating parton, through a phenomenon known as the dead-cone effect, which predicts a suppression of the gluon spectrum emitted by a heavy quark of mass m and energy E, within a cone of angular size m/E around the emitter [3]. A direct observation of the dead-cone effect in QCD has not been possible until now, due to the challenge of reconstructing the cascading quarks and gluons from the experimentally accessible bound hadronic states. Here we show the first direct observation of the QCD dead-cone by using new iterative declustering techniques [4, 5] to reconstruct the parton shower of charm quarks. This result confirms a fundamental feature of QCD, which is derived more generally from its origin as a gauge quantum field theory. Furthermore, the measurement of a dead-cone angle constitutes the first direct experimental observation of the non-zero mass of the charm quark, which is a fundamental constant in the standard model of particle physics.The direct measurement of the QCD dead cone in charm quark fragmentation is reported, using iterative declustering of jets tagged with a fully reconstructed charmed hadron.In particle collider experiments, elementary particle interactions with large momentum transfer produce quarks and gluons (known as partons) whose evolution is governed by the strong force, as described by the theory of quantum chromodynamics (QCD). These partons subsequently emit further partons in a process that can be described as a parton shower which culminates in the formation of detectable hadrons. Studying the pattern of the parton shower is one of the key experimental tools for testing QCD. This pattern is expected to depend on the mass of the initiating parton, through a phenomenon known as the dead-cone effect, which predicts a suppression of the gluon spectrum emitted by a heavy quark of mass $m_{\rm{Q}}$ and energy $E$, within a cone of angular size $m_{\rm{Q}}$/$E$ around the emitter. Previously, a direct observation of the dead-cone effect in QCD had not been possible, owing to the challenge of reconstructing the cascading quarks and gluons from the experimentally accessible hadrons. We report the direct observation of the QCD dead cone by using new iterative declustering techniques to reconstruct the parton shower of charm quarks. This result confirms a fundamental feature of QCD. Furthermore, the measurement of a dead-cone angle constitutes a direct experimental observation of the non-zero mass of the charm quark, which is a fundamental constant in the standard model of particle physics