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1.
Phys Rev Lett ; 131(20): 201801, 2023 Nov 17.
Artículo en Inglés | MEDLINE | ID: mdl-38039482

RESUMEN

A new dark sector antibaryon, denoted ψ_{D}, could be produced in decays of B mesons. This Letter presents a search for B^{+}→ψ_{D}+p (and the charge conjugate) decays in e^{+}e^{-} annihilations at 10.58 GeV, using data collected in the BABAR experiment. Data corresponding to an integrated luminosity of 398 fb^{-1} are analyzed. No evidence for a signal is observed. Branching fraction upper limits in the range from 10^{-7}-10^{-5} are obtained at 90% confidence level for masses of 1.0

2.
Phys Rev Lett ; 128(13): 131802, 2022 Apr 01.
Artículo en Inglés | MEDLINE | ID: mdl-35426701

RESUMEN

Axionlike particles (ALPs) are predicted in many extensions of the standard model, and their masses can naturally be well below the electroweak scale. In the presence of couplings to electroweak bosons, these particles could be emitted in flavor-changing B meson decays. We report herein a search for an ALP, a, in the reaction B^{±}→K^{±}a, a→γγ using data collected by the BABAR experiment at SLAC. No significant signal is observed, and 90% confidence level upper limits on the ALP coupling to electroweak bosons are derived as a function of ALP mass, improving current constraints by several orders of magnitude in the range 0.175 GeV

3.
Phys Rev Lett ; 128(2): 021802, 2022 Jan 14.
Artículo en Inglés | MEDLINE | ID: mdl-35089770

RESUMEN

Collider searches for dark sectors, new particles interacting only feebly with ordinary matter, have largely focused on identifying signatures of new mediators, leaving much of dark sector structures unexplored. In particular, the existence of dark matter bound states (darkonia) remains to be investigated. This possibility could arise in a simple model in which a dark photon (A^{'}) is light enough to generate an attractive force between dark fermions. We report herein a search for a J^{PC}=1^{--} darkonium state, the ϒ_{D}, produced in the reaction e^{+}e^{-}→γϒ_{D}, ϒ_{D}→A^{'}A^{'}A^{'}, where the dark photons subsequently decay into pairs of leptons or pions, using 514 fb^{-1} of data collected with the BABAR detector. No significant signal is observed, and we set bounds on the γ-A^{'} kinetic mixing as a function of the dark sector coupling constant for 0.001

4.
Phys Rev Lett ; 128(9): 091804, 2022 Mar 04.
Artículo en Inglés | MEDLINE | ID: mdl-35302790

RESUMEN

We report on the first search for electron-muon lepton flavor violation (LFV) in the decay of a b quark and b antiquark bound state. We look for the LFV decay ϒ(3S)→e^{±}µ^{∓} in a sample of 118 million ϒ(3S) mesons from 27 fb^{-1} of data collected with the BABAR detector at the SLAC PEP-II e^{+}e^{-} collider operating with a 10.36 GeV center-of-mass energy. No evidence for a signal is found, and we set a limit on the branching fraction B[ϒ(3S)→e^{±}µ^{∓}]<3.6×10^{-7} at 90% C. L. This result can be interpreted as a limit Λ_{NP}/g_{NP}^{2}>80 TeV on the energy scale Λ_{NP} divided by the coupling-squared g_{NP}^{2} of relevant new physics (NP).

5.
Int J Biometeorol ; 66(2): 289-299, 2022 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-34524531

RESUMEN

Numerous climatic indices have been utilized to predict the effect of hot, and cold, climatic conditions on animal production and welfare. To date, the dairy industry has relied extensively on the Temperature Humidity Index (THI) to predict adverse climatic conditions; however, neither solar radiation nor air movement is accounted for in the THI equation. The Dairy Heat Load Index (DHLI) was initially developed as an alternative climate index. In its current format, the DHLI does not account for the effects of heat load mitigation strategies, such as shade, which decreases the negative effects of hot climatic conditions on lactating cows. Therefore, this experiment aimed to determine the effectiveness of the DHLI as a predictor of heat load responses in both shaded and unshaded cows, as compared with the THI. Forty lactating Holstein Friesian (n = 40) cows were selected and paired based on live weight, milk yield, and days in milk. One cow from each pair was randomly allocated to one of two treatments: shaded (n = 20) or unshaded (n = 20). Cows were given 7 days to acclimate prior to the commencement of data collection. After 28 days, cows were transitioned into the alternate treatment in a crossover design and given 7 days to acclimate prior to data collection. Behavioral observations (0800, 1200, 1400, and 1800 h daily), daily milk yield (kg), milk composition (various days), and vaginal temperature (TVAG, °C; 5 pairs/week, over a 4-week rotation) were recorded. Overall, data from this experiment indicated that the DHLI was a better predictor of standing and feeding behaviors in unshaded cows and drinking behaviors in shaded cows. Conversely, the THI was a better predictor of standing behavior and shade usage in shaded cows. Furthermore, the THI was a better predictor of mean panting score (MPS) in shaded cows, whereas the DHLI performed better in unshaded cows. Additionally the DHLI was a better predictor of TVAG in these cows. Finally, when evaluating the 7-day average of each climatic index, the DHLI was a better predictor of change in milk yield. Incorporation of additional animal and management factors is required if the DHLI is to become an effective heat load management tool.


Asunto(s)
Trastornos de Estrés por Calor , Calor , Animales , Bovinos , Estudios Cruzados , Industria Lechera , Femenino , Trastornos de Estrés por Calor/prevención & control , Trastornos de Estrés por Calor/veterinaria , Humedad , Lactancia , Leche
6.
Int J Biometeorol ; 66(2): 275-288, 2022 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-34264388

RESUMEN

The objective of this study was to evaluate the influence of supplementing lactating dairy cows with Saccharomyces cerevisiae on milk production and composition, cow behavior, and physiological responses during summer. Twenty primiparous cows were used and two treatments were imposed: (1) control (CON); and (2) probiotic supplementation (PRO; S. cerevisiae, providing 1010 colony forming units (CFU) per day). Rumen temperature (TRUM, °C) and pH were obtained via rumen boluses. Rumen temperatures were obtained from all cows (n = 20) at 10-min intervals and ruminal pH were obtained from five cow pairs (n = 10) at 10-min intervals. Ambient temperature (TA; °C), relative humidity (RH; %), wind speed (WS; m/s), and solar radiation (SR; W/m2) were recorded at 10-min intervals. The temperature humidity index (THI) was calculated using TA and RH. Cows were milked twice daily. Milk fat (%), protein (%), lactose (%), and somatic cell count (SCC, '000) were evaluated on 16 occasions. Cows were observed three times (0800 h; 1200 h; and 1400 h) daily for panting score (PS); respiration rate (RR); posture (standing/lying); shade utilization; and cow activity (eating/drinking/ruminating). Individual PS were used to calculate a mean panting score (MPS) for CON and PRO treatments for each observation. S. cerevisiae did not influence milk yield (P = 0.87), fat (P = 0.82), protein (P = 0.26) or SCC (P = 0.19), although there was a tendency for PRO cows to have higher lactose (P = 0.06). Probiotics did not influence the proportion of cows utilizing shade (P = 0.42); standing (P = 0.41); ruminating (P = 0.72); or drinking (P = 0.40). All cows exhibited an increase in RR (> 24 bpm) at 1200 h and RR showed a steady increase as THI increased (P < 0.0001), regardless of treatment (P = 0.96). Both CON (35.8%) and PRO (40.2%) exhibited an increase in MPS as THI increased from thermoneutral (THI ≤ 74) to very hot (THI ≥ 84.1; P < 0.001). However, PRO cows had lower (2.19 ± 0.09; P < 0.0001) MPS compared with CON (2.54 ± 0.22) cows when THI was categorized as very hot (THI ≥ 84.1). Rumen pH were not influenced by treatment (P = 0.38), however TRUM of PRO cows were 0.2 °C lower across days (P < 0.0001) and hours (P < 0.0001). These results suggest that supplementing cows with S. cerevisiae may support thermoregulation via decreased TRUM and MPS; however, further studies are required.


Asunto(s)
Lactancia , Saccharomyces cerevisiae , Animales , Bovinos , Dieta/veterinaria , Femenino , Calor , Humedad , Leche
7.
Int J Biometeorol ; 66(2): 251-262, 2022 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-33733303

RESUMEN

The objective of this study was to investigate the effect of acute and chronic heat load events on scrotal temperature (ST), body temperature (BT) and bull behaviour, and to examine the interrelationship between these parameters; the underlying hypothesis was that adverse heat treatments delivered in a temperature controlled environment will lead to thermoregulatory dysfunction of the bull scrotum. Six sexually mature Wagyu bulls were used in this study with data loggers surgically implanted into the abdominal cavity and scrotum. Body temperate and ST were recorded at 30-min intervals for the duration of the study. There were two housing locations used throughout the study, outdoor pens and climate control rooms. The study was designed as a four-phase crossover design with two heat treatments: (1) a 5-day acute challenge, and (2) a 14-day chronic challenge. The study was also blocked by phase to control for systematic change between phases with a thermoneutral (TN) phase in outdoor pens between each heat challenge. Observations within the climate rooms were conducted at 1-h intervals and data on panting scores (PS), respiration rate (RR), posture (standing or lying) and general behaviours (feeding, drinking, ruminating) recorded. Ambient temperature (AT, °C) and relative humidity (RH, %) were obtained at 10-min intervals and used to calculate the temperature humidity index (THI). Multiple models were conducted using a linear mixed effects model that contained different permutations of date and time factors and interactions as well as inclusion of an autoregressive parameter. The strongest model based on Akaike's information criterion (AIC) was selected and further analysed. Ambient conditions during heat treatments were consistent with heat load and bulls showed typical physiological symptoms of the same. Maximum ST for acute and chronic treatments occurred once AT had exceeded 34 °C for at least 3 h (acute 35.59 °C at 1500 h; chronic 35.18 °C at 1400 h), whereas during TN conditions, maximum ST was at 2100 h. All phases showed variation in ST throughout the day. There were strong cross correlations between ST and RR during the heat treatments (acute r = 0.918, P < 0.0001; chronic r = 0.916, P < 0.0001), but not during TN (r = 0.411, P < 0.05). Our results confirmed that the ST of the bulls used in this study was not held at a constant temperature and that there was a possible connection between ST and RR. We have shown that during a period of heat load, the thermoregulatory mechanisms thought responsible for maintaining bovine ST appear to breakdown.


Asunto(s)
Calor , Escroto , Animales , Temperatura Corporal , Regulación de la Temperatura Corporal , Bovinos , Estudios Cruzados , Humedad , Masculino
8.
Bioinformatics ; 35(10): 1766-1767, 2019 05 15.
Artículo en Inglés | MEDLINE | ID: mdl-30295745

RESUMEN

MOTIVATION: Many bioinformatics areas require us to assign domain matches onto stretches of a query protein. Starting with a set of candidate matches, we want to identify the optimal subset that has limited/no overlap between matches. This may be further complicated by discontinuous domains in the input data. Existing tools are increasingly facing very large data-sets for which they require prohibitive amounts of CPU-time and memory. RESULTS: We present cath-resolve-hits (CRH), a new tool that uses a dynamic-programming algorithm implemented in open-source C++ to handle large datasets quickly (up to ∼1 million hits/second) and in reasonable amounts of memory. It accepts multiple input formats and provides its output in plain text, JSON or graphical HTML. We describe a benchmark against an existing algorithm, which shows CRH delivers very similar or slightly improved results and very much improved CPU/memory performance on large datasets. AVAILABILITY AND IMPLEMENTATION: CRH is available at https://github.com/UCLOrengoGroup/cath-tools; documentation is available at http://cath-tools.readthedocs.io. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.


Asunto(s)
Programas Informáticos , Algoritmos , Documentación , Proteínas
9.
Phys Rev Lett ; 125(24): 241801, 2020 Dec 11.
Artículo en Inglés | MEDLINE | ID: mdl-33412062

RESUMEN

We report on a precision measurement of the ratio R_{τµ}^{ϒ(3S)}=B(ϒ(3S)→τ^{+}τ^{-})/B(ϒ(3S)→µ^{+}µ^{-}) using data collected with the BABAR detector at the SLAC PEP-II e^{+}e^{-} collider. The measurement is based on a 28 fb^{-1} data sample collected at a center-of-mass energy of 10.355 GeV corresponding to a sample of 122 million ϒ(3S) mesons. The ratio is measured to be R_{τµ}^{ϒ(3S)}=0.966±0.008_{stat}±0.014_{syst} and is in agreement with the standard model prediction of 0.9948 within 2 standard deviations. The uncertainty in R_{τµ}^{ϒ(3S)} is almost an order of magnitude smaller than the only previous measurement.

10.
Phys Rev Lett ; 125(18): 181801, 2020 Oct 30.
Artículo en Inglés | MEDLINE | ID: mdl-33196250

RESUMEN

Many scenarios of physics beyond the standard model predict the existence of new gauge singlets, which might be substantially lighter than the weak scale. The experimental constraints on additional scalars with masses in the MeV to GeV range could be significantly weakened if they interact predominantly with leptons rather than quarks. At an e^{+}e^{-} collider, such a leptophilic scalar (ϕ_{L}) would be produced predominantly through radiation from a τ lepton. We report herein a search for e^{+}e^{-}→τ^{+}τ^{-}ϕ_{L}, ϕ_{L}→ℓ^{+}ℓ^{-} (ℓ=e, µ) using data collected by the BABAR experiment at SLAC. No significant signal is observed, and we set limits on the ϕ_{L} coupling to leptons in the range 0.04

11.
Phys Rev Lett ; 124(7): 071802, 2020 Feb 21.
Artículo en Inglés | MEDLINE | ID: mdl-32142319

RESUMEN

We present a search for nine lepton-number-violating and three lepton-flavor-violating neutral charm decays of the type D^{0}→h^{'-}h^{-}ℓ^{'+}ℓ^{+} and D^{0}→h^{'-}h^{+}ℓ^{'±}ℓ^{∓}, where h and h^{'} represent a K or π meson and ℓ and ℓ^{'} an electron or muon. The analysis is based on 468 fb^{-1} of e^{+}e^{-} annihilation data collected at or close to the ϒ(4S) resonance with the BABAR detector at the SLAC National Accelerator Laboratory. No significant signal is observed for any of the twelve modes, and we establish 90% confidence level upper limits on the branching fractions in the range (1.0-30.6)×10^{-7}. The limits are between 1 and 3 orders of magnitude more stringent than previous measurements.

12.
Phys Rev Lett ; 124(15): 152001, 2020 Apr 17.
Artículo en Inglés | MEDLINE | ID: mdl-32357020

RESUMEN

A study of the two-body decays B^{±}→X_{cc[over ¯]}K^{±}, where X_{cc[over ¯]} refers to one charmonium state, is reported by the BABAR Collaboration using a data sample of 424 fb^{-1}. The absolute determination of branching fractions for these decays are significantly improved compared to previous BABAR measurements. Evidence is found for the decay B^{+}→X(3872)K^{+} at the 3σ level. The absolute branching fraction B[B^{+}→X(3872)K^{+}]=[2.1±0.6(stat)±0.3(syst)]×10^{-4} is measured for the first time. It follows that B[X(3872)→J/ψπ^{+}π^{-}]=(4.1±1.3)%, supporting the hypothesis of a molecular component for this resonance.

13.
Phys Rev Lett ; 123(9): 091801, 2019 Aug 30.
Artículo en Inglés | MEDLINE | ID: mdl-31524470

RESUMEN

An angular analysis of the decay B[over ¯]→D^{*}ℓ^{-}ν[over ¯]_{ℓ}, ℓ∈{e,µ}, is reported using the full e^{+}e^{-} collision data set collected by the BABAR experiment at the ϒ(4S) resonance. One B meson from the ϒ(4S)→BB[over ¯] decay is fully reconstructed in a hadronic decay mode, which constrains the kinematics and provides a determination of the neutrino momentum vector. The kinematics of the semileptonic decay is described by the dilepton mass squared, q^{2}, and three angles. The first unbinned fit to the full four-dimensional decay rate in the standard model is performed in the so-called Boyd-Grinstein-Lebed approach, which employs a generic q^{2} parametrization of the underlying form factors based on crossing symmetry, analyticity, and QCD dispersion relations for the amplitudes. A fit using the more model-dependent Caprini-Lellouch-Neubert (CLN) approach is performed as well. Our form factor shapes show deviations from previous fits based on the CLN parametrization. The latest form factors also provide an updated prediction for the branching fraction ratio R(D^{*})≡B(B[over ¯]→D^{*}τ^{-}ν[over ¯]_{τ})/B(B[over ¯]→D^{*}ℓ^{-}ν[over ¯]_{ℓ})=0.253±0.005. Finally, using the well-measured branching fraction for the B[over ¯]→D^{*}ℓ^{-}ν[over ¯]_{ℓ} decay, a value of |V_{cb}|=(38.36±0.90)×10^{-3} is obtained that is consistent with the current world average for exclusive B[over ¯]→D^{(*)}ℓ^{-}ν[over ¯]_{ℓ} decays and remains in tension with the determination from inclusive semileptonic B decays to final states with charm.

14.
Phys Rev Lett ; 122(8): 081802, 2019 Mar 01.
Artículo en Inglés | MEDLINE | ID: mdl-30932586

RESUMEN

We report the observation of the rare charm decay D^{0}→K^{-}π^{+}e^{+}e^{-}, based on 468 fb^{-1} of e^{+}e^{-} annihilation data collected at or close to the center-of-mass energy of the ϒ(4S) resonance with the BABAR detector at the SLAC National Accelerator Laboratory. We find the branching fraction in the invariant mass range 0.675

15.
Phys Rev Lett ; 122(7): 072002, 2019 Feb 22.
Artículo en Inglés | MEDLINE | ID: mdl-30848619

RESUMEN

Recent investigations have suggested that the six-quark combination uuddss could be a deeply bound state (S) that has eluded detection so far, and a potential dark matter candidate. We report the first search for a stable, doubly strange six-quark state in ϒ→SΛ[over ¯]Λ[over ¯] decays based on a sample of 90×10^{6}ϒ(2S) and 110×10^{6}ϒ(3S) decays collected by the BABAR experiment. No signal is observed, and 90% confidence level limits on the combined ϒ(2S,3S)→SΛ[over ¯]Λ[over ¯] branching fraction in the range (1.2-1.4)×10^{-7} are derived for m_{S}<2.05 GeV. These bounds set stringent limits on the existence of such exotic particles.

16.
Int J Biometeorol ; 63(7): 939-947, 2019 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-30868342

RESUMEN

This study was conducted to determine the relationship between rectal temperature (TREC) and rumen temperature (TRUM) and to assess if TRUM could be used as a proxy measure of core body temperature (TCORE) in feedlot cattle. Eighty Angus steers (388.8 ± 2.1 kg) were orally administered with rumen temperature boluses. Rumen temperatures were recorded at 10-min intervals over 128 days from all 80 steers. To define the suitability of TRUM as an estimation of TCORE, TREC were obtained from all steers at 7-day intervals (n = 16). Eight feedlot pens were used where there were 10 steers per pen (162 m2). Shade was available in each pen (1.8 m2/animal; 90% solar block). Climatic data were recorded at 30-min intervals, including ambient temperature (TA; °C); relative humidity (RH; %); wind speed (WS; m/s) and direction; solar radiation (SR; W/m2); and black globe temperature (BGT; °C). Rainfall (mm) was recorded daily at 0900 h. From these data, temperature humidity index (THI), heat load index (HLI) and accumulated heat load (AHL) were calculated. Individual 10-min TRUM data were converted to an individual hourly average. Pooled mean hourly TRUM data from the 128-day data were used to establish the diurnal rhythm of TRUM where the mean minimum (39.19 ± 0.01 °C) and mean maximum (40.04 ± 0.01 °C) were observed at 0800 h and 2000 h respectively. A partial correlation coefficient indicated that there were moderate to strong relationships between TRUM and TREC using both real-time (r = 0.55; P < 0.001) and hourly mean (r = 0.51; P < 0.001) TRUM data. The mean difference between TREC and TRUM was small using both real-time (0.16 ± 0.02 °C) and hourly mean TRUM (0.13 ± 0.02 °C) data. Data from this study supports the hypothesis that TRUM can be used as an estimate of TCORE, suggesting that TRUM can be used to measure and quantify heat load in feedlot cattle.


Asunto(s)
Temperatura Corporal , Rumen , Animales , Bovinos , Calor , Humedad , Estaciones del Año , Temperatura
17.
Int J Biometeorol ; 62(1): 3-8, 2018 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-28894980

RESUMEN

Thirty-six Black Angus steers were used in a replicated study; three replicates of 12 steers/replicate. Steers had an initial non-fasted BW of 392.3 ± 5.1, 427.5 ± 6.3, and 392.7 ± 3.7 kg for each replicate, respectively. Steers were housed outside in individual animal pens (10 m × 3.4 m). Each replicate was conducted over a 6-day period where infrared thermography (IRT) images were collected at 3-h intervals, commencing at 0600 h on day 1 and concluding at 0600 h on day 6. Rumen temperatures (T RUM) were measured at 10-min intervals for the duration of each replicate using a radio-frequency identification (RFID) rumen bolus. These data were used to determine the relationship with surface temperature of the cattle, which was determined using IRT. Individual T RUM were converted to an hourly average. The relationship between T RUM and surface temperature was determined using Pearson's correlation coefficient. There were no linear trends between mean hourly T RUM and mean surface temperature. Pearson's correlation coefficient indicated that there were weak associations (r ≤ 0.1; P < 0.003) between T RUM and body surface temperature. These data suggest that there was little relationship between the surface temperature and T RUM.


Asunto(s)
Temperatura Corporal , Bovinos/fisiología , Rumen/fisiología , Termografía/métodos , Animales , Masculino
18.
Int J Biometeorol ; 62(2): 207-215, 2018 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-28918576

RESUMEN

Thirty-six steers (12 of each Angus, Charolais, and Brahman) with an initial BW of 318.5 ± 6.7 kg were used in a 130-day study. Two treatments were imposed: un-shaded and shaded (3 m2/animal; 90% solar block shade cloth). On day 1, steers were administered with rumen temperature boluses. Rumen temperatures (T RUM) were obtained at 10 min intervals over the duration of the study to determine differences in T RUM between Bos indicus and Bos taurus cattle. Six feedlot pens (162 m2) were used with six steers (2/breed) per pen with three pens/treatment. Ambient dry bulb temperature (T A; °C), relative humidity (RH; %), wind speed (WS; m/s) and direction, and solar radiation (SR; W/m2) were recorded at 10 min intervals. Rainfall (mm) was collected daily at 0900 h. From these data, black globe temperature (BGT; °C), temperature humidity index (THI), heat load index (HLI), and accumulated heat load (AHL) were calculated. Individual T RUM were converted to an hourly average and then mean hourly T RUM were converted to a mean within hour T RUM across the 130 days. Rumen temperatures were analyzed using an autoregressive repeated measures model. The model analyzed the effect of breed (P < 0.0002), treatment (P = 0.3543), time of day (hour, h; P < 0.0001), breed × treatment (P < 0.3683), breed × h (P < 0.0001), treatment × h (P < 0.0001), breed × treatment × h (P = 0.0029), pen within treatment (P = 0.0195), and animal × breed × treatment within pen (P = 0.1041). Furthermore, there were breed × treatment × hour differences in T RUM (P = 0.0036), indicating that Bos indicus and Bos taurus regulate T RUM differently.


Asunto(s)
Enfermedades de los Bovinos/fisiopatología , Bovinos/fisiología , Trastornos de Estrés por Calor/fisiopatología , Rumen/fisiología , Animales , Temperatura Corporal , Regulación de la Temperatura Corporal , Trastornos de Estrés por Calor/veterinaria , Calor , Masculino , Especificidad de la Especie
19.
Phys Rev Lett ; 118(3): 031802, 2017 Jan 20.
Artículo en Inglés | MEDLINE | ID: mdl-28157371

RESUMEN

We search for the rare flavor-changing neutral current process B^{+}→K^{+}τ^{+}τ^{-} using data from the BABAR experiment. The data sample, collected at the center-of-mass energy of the ϒ(4S) resonance, corresponds to a total integrated luminosity of 424 fb^{-1} and to 471×10^{6} BB[over ¯] pairs. We reconstruct one B meson, produced in the ϒ(4S)→B^{+}B^{-} decay, in one of many hadronic decay modes and search for activity compatible with a B^{+}→K^{+}τ^{+}τ^{-} decay in the rest of the event. Each τ lepton is required to decay leptonically into an electron or muon and neutrinos. Comparing the expected number of background events with the data sample after applying the selection criteria, we do not find evidence for a signal. The resulting upper limit, at the 90% confidence level, is B(B^{+}→K^{+}τ^{+}τ^{-})<2.25×10^{-3}.

20.
Phys Rev Lett ; 119(13): 131804, 2017 Sep 29.
Artículo en Inglés | MEDLINE | ID: mdl-29341718

RESUMEN

We search for single-photon events in 53 fb^{-1} of e^{+}e^{-} collision data collected with the BABAR detector at the PEP-II B-Factory. We look for events with a single high-energy photon and a large missing momentum and energy, consistent with production of a spin-1 particle A^{'} through the process e^{+}e^{-}→γA^{'}; A^{'}→invisible. Such particles, referred to as "dark photons," are motivated by theories applying a U(1) gauge symmetry to dark matter. We find no evidence for such processes and set 90% confidence level upper limits on the coupling strength of A^{'} to e^{+}e^{-} in the mass range m_{A^{'}}≤8 GeV. In particular, our limits exclude the values of the A^{'} coupling suggested by the dark-photon interpretation of the muon (g-2)_{µ} anomaly, as well as a broad range of parameters for the dark-sector models.

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