What does the star mean in $\rightarrow ZZ^{(∗)}$? Z boson can neither be positive nor negative. &quot;For masses above 130 GeV, Higgs-boson decays, H $\rightarrow ZZ^{(∗)}$, where each Z decays to a pair of oppositely charged leptons, would provide the experimentally cleanest channel to study the properties of the Higgs boson.&quot; Quoted from &quot;The ATLAS Experiment at the CERN Large Hadron Collider&quot;  page 2 or 3
I can always find that in some articles the production of higgs decay written as &quot;$\rm H\to {ZZ}^*\to 4l$&quot;, &quot;$\rm H\to ZZ\to 4l$&quot;, &quot;$\rm H\to Z\gamma^*\to\ldots$” What dose it mean when some particles with a superscript *? Such as “$\rm Z^*, W^*, \gamma^*, \ldots$&quot;. What’s the difference between them and &quot;$\rm Z, W, \gamma$&quot;?
I know that SZ0 makes vertices straightened on the z-axis, but I'm wondering if there's a way to make vertices into a complete circle on the z-axis with a hotkey? Is it possible to check for an injured player in Minecraft? I am creating a mini-game in Minecraft, where I must check to see if the player is injured. The injured player will then be given an item. My guess is that the command would look something like /testfor @p[injured=true], but this command doesn't work. Is there a command for this? Why does Oracle 9i treat an empty string as NULL? Using the Fitch system, how do I prove $((p \implies q) \implies p)\implies p$? I started with the hypotheses $(p \implies q) \implies p$ and $\sim p$. However, from these hypotheses I did not get the desired contradiction to solve the question.  Thanks sb45 Android and getting a view with id cast as a string Why does Python code use len() function instead of a length method? I know that python has a len() function that is used to determine the size of a string, but I was wondering why it's not a method of the string object.  Update  Ok, I realized I was embarrassingly mistaken. __len__() is actually a method of a string object. It just seems weird to see object oriented code in Python using the len function on string objects. Furthermore, it's also weird to see __len__ as the name instead of just len. Installed Teamviewer using a 64-bit system, but I get a dependency error How to import a module given its name as string? I'm writing a Python application that takes as a command as an argument, for example:  $ python myapp.py command1   I want the application to be extensible, that is, to be able to add new modules that implement new commands without having to change the main application source. The tree looks something like:  myapp/     __init__.py     commands/         __init__.py         command1.py         command2.py     foo.py     bar.py   So I want the application to find the available command modules at runtime and execute the appropriate one.  Python defines an __import__ function, which takes a string for a module name:     __import__(name, globals=None, locals=None, fromlist=(), level=0)      The function imports the module name, potentially using the given globals and locals to determine how to interpret the name in a package context. The fromlist gives the names of objects or submodules that should be imported from the module given by name.       Source:    So currently I have something like:  command = sys.argv[1] try:     command_module = __import__("myapp.commands.%s" % command, fromlist=["myapp.commands"]) except ImportError:     # Display error message  command_module.run()   This works just fine, I'm just wondering if there is possibly a more idiomatic way to accomplish what we are doing with this code.  Note that I specifically don't want to get in to using eggs or extension points. This is not an open-source project and I don't expect there to be "plugins". The point is to simplify the main application code and remove the need to modify it each time a new command module is added. Update: Failed to lock /var/cache/apt/archives/lock I am running the upgrade(12.10 to 13.04) through terminal and it keeps getting stuck at this:  Failed to lock /var/cache/apt/archives/lock   What do I do? I have root access. I have no idea what else to try other than a clean install.  Checking package manager Reading package lists... Done     Building dependency tree           Reading state information... Done Building data structures... Done   Calculating the changes Calculating the changes  Do you want to start the upgrade?   3 packages are going to be removed. 155 new packages are going to be  installed. 1204 packages are going to be upgraded.   You have to download a total of 595 M. This download will take about  1 hour 15 minutes with a 1Mbit DSL connection and about 23 hours with  a 56k modem.   Fetching and installing the upgrade can take several hours. Once the  download has finished, the process cannot be canceled.    Continue [yN]  Details [d]y  Fetching  Could not download the upgrades   The upgrade has aborted. Please check your Internet connection or  installation media and try again. All files downloaded so far have  been kept.   Failed to lock /var/cache/apt/archives/lock    Restoring original system state  Aborting Reading package lists... Done     Building dependency tree           Reading state information... Done Building data structures... Done  root@chaitanya-XPS-Ubuntu:~# What does 'exec {fd}</dev/watchdog' do in Bash That is literal, {fd} isn't a placeholder. I have a script that does this, and does not source in anything, nor does it reference {fd} anywhere else.  Is this valid bash?  exec {fd}&lt;/dev/watchdog What does ** (double star/asterisk) and * (star/asterisk) do for parameters? In the following method definitions, what does the * and ** do for param2?  def foo(param1, *param2): def bar(param1, **param2): Why I think tension should be twice the force in a tug of war I'm going to provide my argument for why I think the tension in a rope should be twice the force exerted on either side of it.  First, let's consider a different example. Say, there is a person named A and a block in space. A pushes on the block with a force of 100 N. Then, the block will also push A with a force of 100 N by Newton's third law. Now, consider the case where instead of the block, there is a person B who is also pushing on A with a force of 100 N while A is pushing on him. A will experience a force of 100 N because he pushed on B, AND another 100 N because he is being pushed by B. Hence he will experience a force of 200 N. Similarly, B also experiences 200 N of force.  Now, back to the original problem. There are two people A and B in space with a taut rope (no tension currently) in between them. If only A is pulling and B is not, then I agree that the tension is equal to the force A exerts. This situation (in my opinion) becomes analogous to the above if B is also pulling. So, say both of them pull from either side with a force of 100 N. Then the rope at the end of B will pull B with a force of 100 N (this pull is caused by A). By Newton's third law, the rope will experience a pull of 100 N. But B is also pulling his end of the rope with 100 N. Therefore, the tension should be 200 N. Similarly, the end of the rope at A must pull A with 100 N of force (because B is pulling from the other side) and hence experience a force of 100 N itself by Newton's third law plus another 100 N because A is pulling on the rope.  Apparently, the answer is not this (according to my searching on the web). So, could anyone tell me why this reasoning is wrong? Thanks.  EDIT : So apparently people don't agree with my first example, leave alone the second. This is to the downvoters and the upvoters of the highest-rated answer: You all agree that if only A pushes B with a force of 100 N, then A and B both will get pushed by a force of 100 N in opposite directions, right? Then, in the case where B is also pushing with a force of 100 N, it doesn't make sense that the answer would be exactly the same. It doesn't seem right that no matter what B does, B and A will always experience the same force as they would have if B hadn't applied any force.  EDIT 2 : I'm going to provide here a link to a question that I posted:  According to the answer and the comments there, the reason as to why my first example is incorrect is different to the one provided here. So maybe you should all read the answer and the comments provided by the person and reconsider what you think. What category does the 'the recent perfect' belong to? A scholar has said that there are 4 usages of the present past tense:   The Universal sense of the Perfect, used to indicate that a state of affairs prevailed throughout some interval stretching from the past into the present       I've known Max since 1960.  The Existential sense of the Perfect, used to indicate the existence of past events     I have read Principial Mathematica five times.  The Stative/Resultative sense of the Perfect, used to indicate that the direct effect of a past event still continues     I can't come to your party tonight - I've caught the flu.  The Hot News sense of the Perfect, used to report hot news     Malcolm X has just been assassinated.    To what category does the recent past belong? Proof that the Euler characteristic is additive I'm reading through a set of notes which assumes that the Euler characteristic is additive, but doesn't give a proof, so I would like to understand why this is.  Let $A_n$ be a finitely generated Abelian group, non-zero for $0&lt;n&lt;k$. Consider the long exact sequence  $ \cdots \rightarrow A_n \rightarrow B_n \rightarrow C_n \rightarrow A_{n-1} \rightarrow B_{n-1} \rightarrow C_{n-1} \rightarrow \cdots $  where $B_n$, $C_n$ defined similarly to $A_n$.   I know that the Euler characteristic of $A$ is given by $\chi(A) = \sum_0^k (-1)^n \text{rank}(A_n)$, with similar definitions for $B$ and $C$. I want to prove that $\chi(B) = \chi(A) + \chi(C)$.  The notes say that for an exact sequence  $0 \rightarrow X \rightarrow Y \rightarrow Z \rightarrow 0$  of finitely generated Abelian groups $X,Y,Z$, we have the result rank($Y$) $=$ rank($X$) +  rank($Z$), and that the additivity of the Euler characteristic follows from this fact, but I can't see how. The question at hand is:  "Two capacitors of capacitances $C_1$ and $C_1$ have charge $Q_1$ and $Q_2$. How much energy, $\Delta w$, is dissipated when they are connected in parallel. Show explicitly that $\Delta w$ is non-negative."  I'm confused about what the physical situation is. I took the assumption that these capacitors were somehow pre-charged, and then connected to each other in parallel without a voltage source. However, I don't understand how this would work. If a circuit is composed of only 2 elements, I don't see how they could be in any arrangement but series. Nevertheless, I tried solving it that way:  Two capacitors in parallel have the same voltage drop. Charge will be redistributed to make it the same voltage for both. Let $Q_1'$ and $Q_2'$ be the charges on the capacitors after they are connected. Now, picture the equivalent capacitor  $C_{eq} = C_1 + C_2 =$ $\frac{Q_1' + Q_2'}{V_f}$   conservation of charge:  $Q_1' + Q_2'= Q_1 + Q_2$,        $C_{eq} =$ $\frac{Q_1 + Q_2}{V_f}$  $V_f = $$\frac{Q_1 + Q_2}{C_1 + C_2}$  The initial energy of the capactiors is:  $U_0 = $$\frac{Q_1^2}{2C_1}$$+\frac{Q_2^2}{2C_2}$  $U_f = $$\frac{1}{2}$$(C_1 + C_2)V_f^2 = $$\frac{(Q_1 + Q_2)^2}{2(C_1 + C_2)}$  $\Delta U$$ = $$\frac{(Q_1 + Q_2)^2}{2(C_1 + C_2)}$-$\frac{Q_1^2}{2C_1}$$-\frac{Q_2^2}{2C_2}$  However, I don't see how this is necessarily non-negative. System freezes completely with Intel Bay Trail My system freezes completely at random, frequent intervals. I started to have the same problem in Ubuntu 14.04 but after recent upgrade to 16.04 there is no improvement, in fact it seems worse.  When it happens, it's impossible to do anything. I've tried everything in this thread:  but nothing works, I have to hard reset. I have read all the system logs and journalctl but there is never any information that could help diagnose the problem.  This is a dual-boot system with Windows 10 and there's no problem there, so it's not defective hardware.  My laptop has an Intel Bay Trail processor (Pentium N3540) Group posts by year, then by month Which is correct: "drive safe" or "drive safely"? When someone is going to drive their car somewhere, I always used to say "drive safely" to them. Recently I was told I should say "drive safe."    (From: )   Which one is correct?  Similarly, is "do good" correct? Real Analysis - Prove a set is countable I am asked to prove the following question:  For each finite set of real numbers, $F$, define $\sum F$ to be the sum of all the numbers in $F$.  For each set $P$ of positive real numbers, define $\sum P=\sup\{\sum F: F\text{ is a finite subset of } P\}$.  Suppose $P$ is a set of positive real numbers such that $\sum P &lt; \infty$. Prove that $P$ is a countable set.  My attempt (just a sketch proof):  Suppose $P$ is uncountable, $\exists \epsilon_1 &gt; 0$, s.t. $$ P_1 = [\inf P + \epsilon_1, \sup P]\cap P $$ is uncountable. Pick $a_1 \in [\inf P, \inf P + \epsilon_1] \cap P \in P$, such a $P$ must exists due to greatest lower bound property.  Now $P_1$ is uncountable, $\exists \epsilon_2 &gt; 0$, s.t. $$ P_2 = [\inf P_1 + \epsilon_2, \sup P_1]\cap P_1  $$  is uncountable. Pick $a_2 \in [\inf P_1, \inf P_1 + \epsilon_2]\cap P_1 \in P$. Carry on this process (this should be formalized using induction), we can find  $$ a_1 \leq a_2 \leq a_3 \leq ... $$ with $a_n &gt; 0$ and $a_n \in P$ for all $n$.  Now $\sup\{\sum F_n: F_n = \{a_1,...,a_n\}, n \in \mathbb{N}^+\} = \lim_{n \to \infty}\sum_{i = 1}^n a_i &gt; \lim_{n \to \infty}na_1 = \infty$. This means that $\sum P = \infty$ since $\{\sum F_n: F_n = \{a_1,...,a_n\}, n \in \mathbb{N}^+\} \subset \{\sum F: F\text{ is a finite subset of } P\}$.  I think my proof is a bit clumsy but is it correct? Why does my apple not weigh 500 tons? Related to this question:   $E=mc^2$ - energy equals mass. So, if an object has gravitational potential energy relative to another object, it should have additional mass to represent that extra energy.  So, if I have an apple in my hand, it should have quite a large amount of gravitational potential energy relative to a black hole at the edge of the observable universe. I did a quick calculation of how much this gravitational potential energy would be (using Newton's Law of Gravitation) and it came out to be the equivalent of around 500 tons (and that's just for one black hole!).  So, why does my apple not weigh a lot more than it appears to?  EDIT: Here's my calculation of the GPE:  Assumptions:   The apple has mass $m_a=0.3 kg$ The black hole has a mass equal to 1000 solar masses, $m_b=2\times10^{33} kg$ Distance between the apple and black hole is 60 billion light years   Obviously $GPE=mgh$ can't be used, because the gravitational acceleration is not constant and varies with distance, so it has to be integrated.  I used Newton's Law of Gravitation to provide the acceleration:  $$ F=\frac{G{m_1}{m_2}}{h^2} $$  A small change in height produces a small change in energy, which can be used to integrate:  $$ \begin{eqnarray*} \delta E&amp;=&amp;F \delta h\\ \int_0^EdE&amp;=&amp;G{m_a}{m_b}\int_1^R\frac{1}{h^2}dh \end{eqnarray*} $$  I'm integrating the force starting at 1m from the center of the black hole, as the force goes to infinity at $h=0$. It's a little crude, but it should provide a conservative estimate.  $$ \begin{eqnarray*} E&amp;=&amp;G{m_a}{m_b}(1-\frac{1}{R})\\ E&amp;\approx&amp; G{m_a}{m_b}\;\;\;\;\;\;(R&gt;&gt;1)\\ G&amp;=&amp;6.673\times 10^{-11}\;\;N(\frac{m}{kg})^2\\ G{m_a}{m_b}&amp;=&amp;4\times 10^{22}\;\;Nm\\ E&amp;=&amp;mc^2\\ \Delta m&amp;=&amp;\frac{4\times 10^{22}}{(3\times 10^8)^2}\\ &amp;\approx&amp;444,000\;\;kg \end{eqnarray*} $$  So, a little short of 500 tons, but still pretty big!