arXiv subjects

A. Pearce

Publications and source records attributed to A. Pearce.

8 recordsLinked to original sources

arXiv2019

Design and performance of the LHCb trigger and full real-time reconstruction in Run 2 of the LHC

The LHCb collaboration has redesigned its trigger to enable the full offline detector reconstruction to be performed in real time. Together with the real-time alignment and calibration of the detector, and a software infrastructure to make persistent the high-level physics objects produced during real-time processing, this redesign enabled the widespread deployment of real-time analysis during Run 2. We describe the design of the Run 2 trigger and real-time reconstruction, and present data-driven performance measurements for a representative sample of LHCb's physics programme.

hep-ex↗

arXiv2019

A comprehensive real-time analysis model at the LHCb experiment

An evolved real-time data processing strategy is proposed for high-energy physics experiments, and its implementation at the LHCb experiment is presented. The reduced event model allows not only the signal candidate firing the trigger to be persisted, as previously available, but also an arbitrary set of other reconstructed or raw objects from the event. This allows for higher trigger rates for a given output data bandwidth, when compared to the traditional model of saving the full raw detector data for each trigger, whilst accommodating inclusive triggers and preserving data mining capabilities. The gains in physics reach and savings in computing resources already made possible by the model are discussed, along with the prospects of employing it more widely for Run 3 of the Large Hadron Collider.

hep-ex↗

arXiv2018

Mapping the material in the LHCb vertex locator using secondary hadronic interactions

Precise knowledge of the location of the material in the LHCb vertex locator (VELO) is essential to reducing background in searches for long-lived exotic particles, and in identifying jets that originate from beauty and charm quarks. Secondary interactions of hadrons produced in beam-gas collisions are used to map the location of material in the VELO. Using this material map, along with properties of a reconstructed secondary vertex and its constituent tracks, a $p$-value can be assigned to the hypothesis that the secondary vertex originates from a material interaction. A validation of this procedure is presented using photon conversions to dimuons.

physics.ins-det↗

arXiv2003

Photometric study of new southern SU UMa-type dwarf novae - II: Authentication of BF Ara as a Normal SU UMa-type Dwarf Nova with the Shortest Supercycle

We photometrically observed the 2002 August long outburst of BF Ara. The observation for the first time unambiguously detected superhumps (average period 0.08797(1) d), qualifying BF Ara as a genuine SU UMa-type dwarf nova. An analysis of the long-term visual light curve yielded a mean supercycle length of 84.3(3) d. The characteristics of outbursts and superhumps more resemble those of usual SU UMa-type dwarf novae rather than those of ER UMa stars. BF Ara is thus confirmed to be the usual SU UMa-type dwarf nova with the shortest known supercycle length. There still remains an unfilled gap of distributions between ER UMa stars and usual SU UMa-type dwarf novae. We detected a zero period change of the superhumps, which is quite unexpected from our previous knowledge. This discovery implies that a previous interpretation requiring a low M-dot would be no longer valid, or that a different mechanism is responsible for BF Ara. We propose that the reduced (prograde) apsidal motion of the eccentric disk by pressure forces may be responsible for the unusual period change in BF Ara.

astro-ph↗

arXiv2002

Photometric study of new southern SU UMa-type dwarf novae and candidates: V877 Ara, KK Tel and PU CMa

We photometrically observed three dwarf novae V877 Ara, KK Tel and PU CMa. We discovered undisputed presence of superhumps in V877 Ara and KK Tel, with mean periods of 0.08411(2) d and 0.08808(3) d, respectively. Both V877 Ara and KK Tel are confirmed to belong to long-period SU UMa-type dwarf novae. In V877 Ara, we found a large decrease of the superhump period (dot(P)/P = -14.5 +/- 2.1 x 10^(-5)). There is evidence that the period of KK Tel decreased at a similar or a more exceptional rate. Coupled with the past studies of superhump period changes, these findings suggest that a previously neglected diversity of phenomena is present in long-period SU UMa-type dwarf novae. The present discovery of a diversity in long-period SU UMa-type systems would become an additional step toward a full understanding the dwarf nova phenomenon. PU CMa is shown to be an excellent candidate for an SU UMa-type dwarf nova. We examined the outburst properties of these dwarf novae, and derived characteristic outburst recurrence times. Combined with the recently published measurement of the orbital period of PU CMa, we propose that PU CMa is the first object filling the gap between the extreme WZ Sge-type and ER UMa-type stars.

astro-ph↗

arXiv2002

Two X-Ray Bright Cataclysmic Variables with Unusual Activities: GZ Cnc and NSV 10934

We report on a discovery of unexpected activities in two X-ray bright dwarf novae. GZ Cnc showed an anomalous clustering of outbursts in 2002, in contrast to a low outburst frequency in the past record. The activity resembles an increased activity seen in some intermediate polars or candidates. We identified NSV 10934, X-ray selected high-amplitude variable star, as a dwarf nova with unusually rapid decline. The outburst characteristics make NSV 10934 a twin of recently discovered intermediate polar (HT Cam) with dwarf nova-type outbursts. We propose that these activities in X-ray strong dwarf novae may be a previously overlooked manifestation of outburst activities in magnetic cataclysmic variables.

astro-ph↗

arXiv2002

NSV 10934: an Unusual ROSAT-Selected Dwarf Nova: An Analogous Object to HT Cam?

NSV 10934 was discovered as a large-amplitude suspected variable star of unknown classification. We noticed that the object is identified with a bright ROSAT X-ray source (1RXS J184050.3-834305). Systematic monitoring of this object by the VSNET team revealed four outbursts between 2001 and 2002, confirming the dwarf nova-type nature of NSV 10934. The outbursts were characterized by a rapid fading (1.5 mag within 0.90 d) toward the end of the outbursts. Combined with the strong and relatively hard X-ray detection, this outburst behavior suggests that the object may be related to the recently discovered intermediate polar, HT Cam (astro-ph/0206184).

astro-ph↗

arXiv1999

The 1999 outburst of the eclipsing and recurrent nova U Scorpii

The spectroscopic and photometric evolution of the 1999 outburst of the eclipsing and recurrent nova U Sco is presented. The photometric evolution closely matches that of the previous events. The FWZI=10,000 km/sec for emission lines at maximum has decreased to 4000 km/sec by day +23, with continuous and dramatic changes in the line profiles. No nebular line has become visible and the ionization degree has increased during the brightness decline. A not previously reported and quite puzzling splitting of the emission lines into three components after the first two weeks is outstanding in our spectra. The radiated luminosity is found to be a tiny fraction of that of classical novae for any reasonable distance to U Sco.

astro-ph↗